diff --git a/samples/ControlCatalog/Pages/DialogsPage.xaml b/samples/ControlCatalog/Pages/DialogsPage.xaml
index 710d791f3a..23b14d009d 100644
--- a/samples/ControlCatalog/Pages/DialogsPage.xaml
+++ b/samples/ControlCatalog/Pages/DialogsPage.xaml
@@ -3,10 +3,6 @@
       <Button Name="OpenFile">Open File</Button>
       <Button Name="SaveFile">Save File</Button>
       <Button Name="SelectFolder">Select Folder</Button>
-      <StackPanel Orientation="Horizontal">
-          <CheckBox Name="IsModal" IsChecked="True"/>
-          <TextBlock>Modal to window</TextBlock>
-      </StackPanel>
       <Button Name="DecoratedWindow">Decorated window</Button>
   </StackPanel>
 </UserControl>
diff --git a/samples/ControlCatalog/Pages/DialogsPage.xaml.cs b/samples/ControlCatalog/Pages/DialogsPage.xaml.cs
index 8b3e810f0a..f215bf9e64 100644
--- a/samples/ControlCatalog/Pages/DialogsPage.xaml.cs
+++ b/samples/ControlCatalog/Pages/DialogsPage.xaml.cs
@@ -31,12 +31,12 @@ namespace ControlCatalog.Pages
                 }.ShowAsync(GetWindow());
             };
             this.FindControl<Button>("DecoratedWindow").Click += delegate
-            {
-                new DecoratedWindow().Show();
-            };
+                {
+                    new DecoratedWindow().ShowDialog(GetWindow());
+                };
         }
 
-        Window GetWindow() => this.FindControl<CheckBox>("IsModal").IsChecked.Value ? (Window)this.VisualRoot : null;
+        Window GetWindow() => (Window)this.VisualRoot;
 
         private void InitializeComponent()
         {
diff --git a/samples/ControlCatalog/Pages/MenuPage.xaml.cs b/samples/ControlCatalog/Pages/MenuPage.xaml.cs
index ec7c000fe6..5a07cae89f 100644
--- a/samples/ControlCatalog/Pages/MenuPage.xaml.cs
+++ b/samples/ControlCatalog/Pages/MenuPage.xaml.cs
@@ -83,7 +83,7 @@ namespace ControlCatalog.Pages
         public async Task Open()
         {
             var dialog = new OpenFileDialog();
-            var result = await dialog.ShowAsync();
+            var result = await dialog.ShowAsync(App.Current.MainWindow);
 
             if (result != null)
             {
diff --git a/src/Avalonia.Controls/Platform/IWindowImpl.cs b/src/Avalonia.Controls/Platform/IWindowImpl.cs
index f1f3925133..2ddc5a5c85 100644
--- a/src/Avalonia.Controls/Platform/IWindowImpl.cs
+++ b/src/Avalonia.Controls/Platform/IWindowImpl.cs
@@ -30,10 +30,7 @@ namespace Avalonia.Platform
         /// <summary>
         /// Shows the window as a dialog.
         /// </summary>
-        /// <returns>
-        /// An <see cref="IDisposable"/> that should be used to close the window.
-        /// </returns>
-        IDisposable ShowDialog();
+        void ShowDialog(IWindowImpl parent);
 
         /// <summary>
         /// Enables or disables system window decorations (title bar, buttons, etc)
diff --git a/src/Avalonia.Controls/SystemDialog.cs b/src/Avalonia.Controls/SystemDialog.cs
index 9a739d6556..e7cb4763ed 100644
--- a/src/Avalonia.Controls/SystemDialog.cs
+++ b/src/Avalonia.Controls/SystemDialog.cs
@@ -1,3 +1,4 @@
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Threading.Tasks;
@@ -18,28 +19,40 @@ namespace Avalonia.Controls
 
     public class SaveFileDialog : FileDialog
     {
-        public string DefaultExtension { get; set; }        
+        public string DefaultExtension { get; set; }
 
-        public async Task<string> ShowAsync(Window window)
-            =>
-                ((await AvaloniaLocator.Current.GetService<ISystemDialogImpl>().ShowFileDialogAsync(this, window?.PlatformImpl)) ??
-                 new string[0]).FirstOrDefault();
+        public async Task<string> ShowAsync(Window parent)
+        {
+            if(parent == null)
+                throw new ArgumentNullException(nameof(parent));
+            return ((await AvaloniaLocator.Current.GetService<ISystemDialogImpl>()
+                 .ShowFileDialogAsync(this, parent?.PlatformImpl)) ??
+             new string[0]).FirstOrDefault();
+        }
     }
 
     public class OpenFileDialog : FileDialog
     {
         public bool AllowMultiple { get; set; }
 
-        public Task<string[]> ShowAsync(Window window = null)
-            => AvaloniaLocator.Current.GetService<ISystemDialogImpl>().ShowFileDialogAsync(this, window?.PlatformImpl);
+        public Task<string[]> ShowAsync(Window parent)
+        {
+            if(parent == null)
+                throw new ArgumentNullException(nameof(parent));
+            return AvaloniaLocator.Current.GetService<ISystemDialogImpl>().ShowFileDialogAsync(this, parent?.PlatformImpl);
+        }
     }
 
     public class OpenFolderDialog : FileSystemDialog
     {
         public string DefaultDirectory { get; set; }
 
-        public Task<string> ShowAsync(Window window = null)
-               => AvaloniaLocator.Current.GetService<ISystemDialogImpl>().ShowFolderDialogAsync(this, window?.PlatformImpl);
+        public Task<string> ShowAsync(Window parent)
+        {
+            if(parent == null)
+                throw new ArgumentNullException(nameof(parent));
+            return AvaloniaLocator.Current.GetService<ISystemDialogImpl>().ShowFolderDialogAsync(this, parent?.PlatformImpl);
+        }
     }
 
     public abstract class SystemDialog
diff --git a/src/Avalonia.Controls/Window.cs b/src/Avalonia.Controls/Window.cs
index 39b4f05545..46916efc1d 100644
--- a/src/Avalonia.Controls/Window.cs
+++ b/src/Avalonia.Controls/Window.cs
@@ -397,11 +397,23 @@ namespace Avalonia.Controls
         /// <returns>
         /// A task that can be used to track the lifetime of the dialog.
         /// </returns>
-        public Task ShowDialog()
+        public Task ShowDialog(Window parent)
         {
-            return ShowDialog<object>();
+            return ShowDialog<object>(parent);
         }
 
+
+        /// <summary>
+        /// Shows the window as a dialog.
+        /// </summary>
+        /// <typeparam name="TResult">
+        /// The type of the result produced by the dialog.
+        /// </typeparam>
+        /// <returns>.
+        /// A task that can be used to retrieve the result of the dialog when it closes.
+        /// </returns>
+        public Task<TResult> ShowDialog<TResult>(Window parent) => ShowDialog<TResult>(parent.PlatformImpl);
+        
         /// <summary>
         /// Shows the window as a dialog.
         /// </summary>
@@ -411,8 +423,10 @@ namespace Avalonia.Controls
         /// <returns>.
         /// A task that can be used to retrieve the result of the dialog when it closes.
         /// </returns>
-        public Task<TResult> ShowDialog<TResult>()
+        public Task<TResult> ShowDialog<TResult>(IWindowImpl parent)
         {
+            if(parent == null)
+                throw new ArgumentNullException(nameof(parent));
             if (IsVisible)
             {
                 throw new InvalidOperationException("The window is already being shown.");
@@ -427,24 +441,18 @@ namespace Avalonia.Controls
 
             using (BeginAutoSizing())
             {
-                var affectedWindows = Application.Current.Windows.Where(w => w.IsEnabled && w != this).ToList();
-                var activated = affectedWindows.Where(w => w.IsActive).FirstOrDefault();
-                SetIsEnabled(affectedWindows, false);
 
-                var modal = PlatformImpl?.ShowDialog();
+                PlatformImpl?.ShowDialog(parent);
                 var result = new TaskCompletionSource<TResult>();
 
                 Renderer?.Start();
-
                 Observable.FromEventPattern<EventHandler, EventArgs>(
                     x => this.Closed += x,
                     x => this.Closed -= x)
                     .Take(1)
                     .Subscribe(_ =>
                     {
-                        modal?.Dispose();
-                        SetIsEnabled(affectedWindows, true);
-                        activated?.Activate();
+                        parent.Activate();
                         result.SetResult((TResult)(_dialogResult ?? default(TResult)));
                     });
 
@@ -452,14 +460,6 @@ namespace Avalonia.Controls
             }
         }
 
-        void SetIsEnabled(IEnumerable<Window> windows, bool isEnabled)
-        {
-            foreach (var window in windows)
-            {
-                window.IsEnabled = isEnabled;
-            }
-        }
-
         void SetWindowStartupLocation()
         {
             if (WindowStartupLocation == WindowStartupLocation.CenterScreen)
diff --git a/src/Avalonia.DesignerSupport/Remote/PreviewerWindowImpl.cs b/src/Avalonia.DesignerSupport/Remote/PreviewerWindowImpl.cs
index ed2c55895c..cff59f2f8b 100644
--- a/src/Avalonia.DesignerSupport/Remote/PreviewerWindowImpl.cs
+++ b/src/Avalonia.DesignerSupport/Remote/PreviewerWindowImpl.cs
@@ -86,9 +86,8 @@ namespace Avalonia.DesignerSupport.Remote
         {
         }
 
-        public IDisposable ShowDialog()
+        public void ShowDialog(IWindowImpl parent)
         {
-            return Disposable.Empty;
         }
 
         public void SetSystemDecorations(bool enabled)
@@ -111,4 +110,4 @@ namespace Avalonia.DesignerSupport.Remote
         {
         }
     }
-}
\ No newline at end of file
+}
diff --git a/src/Avalonia.DesignerSupport/Remote/Stubs.cs b/src/Avalonia.DesignerSupport/Remote/Stubs.cs
index 3a97b0d799..8f5b97af41 100644
--- a/src/Avalonia.DesignerSupport/Remote/Stubs.cs
+++ b/src/Avalonia.DesignerSupport/Remote/Stubs.cs
@@ -87,7 +87,9 @@ namespace Avalonia.DesignerSupport.Remote
         {
         }
 
-        public IDisposable ShowDialog() => Disposable.Empty;
+        public void ShowDialog(IWindowImpl parent)
+        {
+        }
 
         public void SetSystemDecorations(bool enabled)
         {
@@ -157,4 +159,4 @@ namespace Avalonia.DesignerSupport.Remote
         public Screen[] AllScreens { get; } =
             {new Screen(new Rect(0, 0, 4000, 4000), new Rect(0, 0, 4000, 4000), true)};
     }
-}
\ No newline at end of file
+}
diff --git a/src/Avalonia.Native/WindowImpl.cs b/src/Avalonia.Native/WindowImpl.cs
index 5d30408e52..a05febddf1 100644
--- a/src/Avalonia.Native/WindowImpl.cs
+++ b/src/Avalonia.Native/WindowImpl.cs
@@ -46,9 +46,9 @@ namespace Avalonia.Native
 
         public IAvnWindow Native => _native;
 
-        public IDisposable ShowDialog()
+        public void ShowDialog(IWindowImpl window)
         {
-            return _native.ShowDialog();
+            _native.ShowDialog();
         }
 
         public void CanResize(bool value)
diff --git a/src/Gtk/Avalonia.Gtk3/Interop/Native.cs b/src/Gtk/Avalonia.Gtk3/Interop/Native.cs
index 98a73a98a9..bf973119a9 100644
--- a/src/Gtk/Avalonia.Gtk3/Interop/Native.cs
+++ b/src/Gtk/Avalonia.Gtk3/Interop/Native.cs
@@ -67,6 +67,9 @@ namespace Avalonia.Gtk3.Interop
 
             [UnmanagedFunctionPointer(CallingConvention.Cdecl), GtkImport(GtkDll.Gtk)]
             public delegate void gtk_window_set_modal(GtkWindow window, bool modal);
+            
+            [UnmanagedFunctionPointer(CallingConvention.Cdecl), GtkImport(GtkDll.Gtk)]
+            public delegate void gtk_window_set_transient_for(GtkWindow window, IntPtr parent);
 
             [UnmanagedFunctionPointer(CallingConvention.Cdecl)] //No manual import
             public delegate IntPtr gdk_get_native_handle(IntPtr gdkWindow);
@@ -408,6 +411,7 @@ namespace Avalonia.Gtk3.Interop
         public static D.gtk_window_new GtkWindowNew;
         public static D.gtk_window_set_icon GtkWindowSetIcon;
         public static D.gtk_window_set_modal GtkWindowSetModal;
+        public static D.gtk_window_set_transient_for GtkWindowSetTransientFor;
         public static D.gdk_set_allowed_backends GdkSetAllowedBackends;
         public static D.gtk_init GtkInit;
         public static D.gtk_window_present GtkWindowPresent;
diff --git a/src/Gtk/Avalonia.Gtk3/WindowBaseImpl.cs b/src/Gtk/Avalonia.Gtk3/WindowBaseImpl.cs
index 0273f6a7d8..8db8a74e07 100644
--- a/src/Gtk/Avalonia.Gtk3/WindowBaseImpl.cs
+++ b/src/Gtk/Avalonia.Gtk3/WindowBaseImpl.cs
@@ -422,7 +422,7 @@ namespace Avalonia.Gtk3
             Native.GdkWindowSetCursor(Native.GtkWidgetGetWindow(GtkWidget), cursor?.Handle ??  IntPtr.Zero);
         }
 
-        public void Show() => Native.GtkWindowPresent(GtkWidget);
+        public virtual void Show() => Native.GtkWindowPresent(GtkWidget);
 
         public void Hide() => Native.GtkWidgetHide(GtkWidget);
 
diff --git a/src/Gtk/Avalonia.Gtk3/WindowImpl.cs b/src/Gtk/Avalonia.Gtk3/WindowImpl.cs
index 34950ca8b8..1c8d800f2f 100644
--- a/src/Gtk/Avalonia.Gtk3/WindowImpl.cs
+++ b/src/Gtk/Avalonia.Gtk3/WindowImpl.cs
@@ -63,11 +63,18 @@ namespace Avalonia.Gtk3
 
         public Action<WindowState> WindowStateChanged { get; set; }
 
-        public IDisposable ShowDialog()
+        public void ShowDialog(IWindowImpl parent)
         {
             Native.GtkWindowSetModal(GtkWidget, true);
-            Show();
-            return new EmptyDisposable();
+            Native.GtkWindowSetTransientFor(GtkWidget, ((WindowImpl)parent).GtkWidget.DangerousGetHandle());
+            Native.GtkWindowPresent(GtkWidget);
+        }
+
+        public override void Show()
+        {
+            Native.GtkWindowSetModal(GtkWidget, false);
+            Native.GtkWindowSetTransientFor(GtkWidget, IntPtr.Zero);
+            Native.GtkWindowPresent(GtkWidget);
         }
 
         public void SetSystemDecorations(bool enabled) => Native.GtkWindowSetDecorated(GtkWidget, enabled);
diff --git a/src/Windows/Avalonia.Win32/Interop/UnmanagedMethods.cs b/src/Windows/Avalonia.Win32/Interop/UnmanagedMethods.cs
index f33b239dc6..9e8ff20e44 100644
--- a/src/Windows/Avalonia.Win32/Interop/UnmanagedMethods.cs
+++ b/src/Windows/Avalonia.Win32/Interop/UnmanagedMethods.cs
@@ -780,8 +780,8 @@ namespace Avalonia.Win32.Interop
         [DllImport("user32.dll", SetLastError = true, EntryPoint = "SetWindowLong")]
         private static extern uint SetWindowLong32b(IntPtr hWnd, int nIndex, uint value);
 
-        [DllImport("user32.dll", SetLastError = true)]
-        private static extern uint SetWindowLongPtr(IntPtr hWnd, int nIndex, uint value);
+        [DllImport("user32.dll", SetLastError = true, EntryPoint = "SetWindowLongPtr")]
+        private static extern IntPtr SetWindowLong64b(IntPtr hWnd, int nIndex, IntPtr value);
 
         public static uint SetWindowLong(IntPtr hWnd, int nIndex, uint value)
         {
@@ -791,7 +791,19 @@ namespace Avalonia.Win32.Interop
             }
             else
             {
-                return SetWindowLongPtr(hWnd, nIndex, value);
+                return (uint)SetWindowLong64b(hWnd, nIndex, new IntPtr((uint)value)).ToInt32();
+            }
+        }
+        
+        public static IntPtr SetWindowLongPtr(IntPtr hWnd, int nIndex, IntPtr handle)
+        {
+            if (IntPtr.Size == 4)
+            {
+                return new IntPtr(SetWindowLong32b(hWnd, nIndex, (uint)handle.ToInt32()));
+            }
+            else
+            {
+                return SetWindowLong64b(hWnd, nIndex, handle);
             }
         }
 
diff --git a/src/Windows/Avalonia.Win32/WindowImpl.cs b/src/Windows/Avalonia.Win32/WindowImpl.cs
index 21986bd2ba..e4f15382ea 100644
--- a/src/Windows/Avalonia.Win32/WindowImpl.cs
+++ b/src/Windows/Avalonia.Win32/WindowImpl.cs
@@ -42,6 +42,8 @@ namespace Avalonia.Win32
         private OleDropTarget _dropTarget;
         private Size _minSize;
         private Size _maxSize;
+        private WindowImpl _parent;
+        private readonly List<WindowImpl> _disabledBy = new List<WindowImpl>();
 
 #if USE_MANAGED_DRAG
         private readonly ManagedWindowResizeDragHelper _managedDrag;
@@ -165,10 +167,10 @@ namespace Avalonia.Win32
             private set;
         }
 
-        public bool IsEnabled
+
+        void UpdateEnabled()
         {
-            get { return UnmanagedMethods.IsWindowEnabled(_hwnd); }
-            set { UnmanagedMethods.EnableWindow(_hwnd, value); }
+            EnableWindow(_hwnd, _disabledBy.Count == 0);
         }
 
         public Size MaxClientSize
@@ -248,6 +250,12 @@ namespace Avalonia.Win32
 
         public void Hide()
         {
+            if (_parent != null)
+            {
+                _parent._disabledBy.Remove(this);
+                _parent.UpdateEnabled();
+                _parent = null;
+            }
             UnmanagedMethods.ShowWindow(_hwnd, UnmanagedMethods.ShowWindowCommand.Hide);
         }
 
@@ -359,6 +367,7 @@ namespace Avalonia.Win32
 
         public virtual void Show()
         {
+            SetWindowLongPtr(_hwnd, (int)WindowLongParam.GWL_HWNDPARENT, IntPtr.Zero);
             ShowWindow(_showWindowState);
         }
 
@@ -412,11 +421,13 @@ namespace Avalonia.Win32
             }
         }
 
-        public virtual IDisposable ShowDialog()
+        public void ShowDialog(IWindowImpl parent)
         {
-            Show();
-
-            return Disposable.Empty;
+            _parent = (WindowImpl)parent;
+            _parent._disabledBy.Add(this);
+            _parent.UpdateEnabled();
+            SetWindowLongPtr(_hwnd, (int)WindowLongParam.GWL_HWNDPARENT, ((WindowImpl)parent)._hwnd);
+            ShowWindow(_showWindowState);
         }
 
         public void SetCursor(IPlatformHandle cursor)
diff --git a/tests/Avalonia.Controls.UnitTests/WindowTests.cs b/tests/Avalonia.Controls.UnitTests/WindowTests.cs
index 570cebe0e5..adf9bd9cec 100644
--- a/tests/Avalonia.Controls.UnitTests/WindowTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/WindowTests.cs
@@ -62,9 +62,11 @@ namespace Avalonia.Controls.UnitTests
         {
             using (UnitTestApplication.Start(TestServices.StyledWindow))
             {
+                var parent = new Window();
+                parent.Show();
                 var window = new Window();
 
-                var task = window.ShowDialog();
+                var task = window.ShowDialog(parent);
 
                 Assert.True(window.IsVisible);
             }
@@ -258,12 +260,13 @@ namespace Avalonia.Controls.UnitTests
         {
             using (UnitTestApplication.Start(TestServices.StyledWindow))
             {
+                var parent = new Mock<IWindowImpl>();
                 var windowImpl = new Mock<IWindowImpl>();
                 windowImpl.SetupProperty(x => x.Closed);
                 windowImpl.Setup(x => x.Scaling).Returns(1);
 
                 var target = new Window(windowImpl.Object);
-                var task = target.ShowDialog<bool>();
+                var task = target.ShowDialog<bool>(parent.Object);
 
                 windowImpl.Object.Closed();