diff --git a/src/msw/toplevel.cpp b/src/msw/toplevel.cpp
index 0ddfefcbe6..62e6c91c4f 100644
--- a/src/msw/toplevel.cpp
+++ b/src/msw/toplevel.cpp
@@ -451,10 +451,11 @@ bool wxTopLevelWindowMSW::Create(wxWindow *parent,
         memset(dlgTemplate, 0, dlgsize);
 
         // these values are arbitrary, they won't be used normally anyhow
-        dlgTemplate->x  = 34;
+        const LONG baseUnits = ::GetDialogBaseUnits();
+        dlgTemplate->x = 34;
         dlgTemplate->y  = 22;
-        dlgTemplate->cx = 144;
-        dlgTemplate->cy = 75;
+        dlgTemplate->cx = ::MulDiv(sizeReal.x, 4, LOWORD(baseUnits));
+        dlgTemplate->cy = ::MulDiv(sizeReal.y, 8, HIWORD(baseUnits));
 
         // reuse the code in MSWGetStyle() but correct the results slightly for
         // the dialog
diff --git a/src/msw/window.cpp b/src/msw/window.cpp
index b2cd66a7dc..a76d66c1f1 100644
--- a/src/msw/window.cpp
+++ b/src/msw/window.cpp
@@ -1822,6 +1822,26 @@ wxWindowMSW::DoMoveSibling(WXHWND hwnd, int x, int y, int width, int height)
 
     // otherwise (or if deferring failed) move the window in place immediately
 #endif // wxUSE_DEFERRED_SIZING
+
+    // toplevel window's coordinates are mirrored if the TLW is a child of another
+    // RTL window and changing width without moving the position would enlarge the
+    // window in the wrong direction, so we need to adjust for it
+    if ( IsTopLevel() )
+    {
+        // note that this may be different from GetParent() for wxDialogs
+        HWND tlwParent = ::GetParent((HWND)hwnd);
+        if ( tlwParent && (::GetWindowLong(tlwParent, GWL_EXSTYLE) & WS_EX_LAYOUTRTL) != 0 )
+        {
+            RECT old;
+            ::GetWindowRect((HWND) hwnd, &old);
+            if ( old.left == x && old.right - old.left != width )
+            {
+                x -= width - (old.right - old.left);
+            }
+            // else: not a simple resize
+        }
+    }
+
     if ( !::MoveWindow((HWND)hwnd, x, y, width, height, IsShown()) )
     {
         wxLogLastError(wxT("MoveWindow"));
@@ -1967,10 +1987,25 @@ void wxWindowMSW::DoSetClientSize(int width, int height)
         const int widthWin = rectWin.right - rectWin.left,
                   heightWin = rectWin.bottom - rectWin.top;
 
-        // MoveWindow positions the child windows relative to the parent, so
-        // adjust if necessary
-        if ( !IsTopLevel() )
+        if ( IsTopLevel() )
         {
+            // toplevel window's coordinates are mirrored if the TLW is a child of another
+            // RTL window and changing width without moving the position would enlarge the
+            // window in the wrong direction, so we need to adjust for it
+
+            // note that this may be different from GetParent() for wxDialogs
+            HWND tlwParent = ::GetParent(GetHwnd());
+            if ( tlwParent && (::GetWindowLong(tlwParent, GWL_EXSTYLE) & WS_EX_LAYOUTRTL) != 0 )
+            {
+                const int diffWidth = width - (rectClient.right - rectClient.left);
+                rectWin.left -= diffWidth;
+                rectWin.right -= diffWidth;
+            }
+        }
+        else
+        {
+            // MoveWindow positions the child windows relative to the parent, so
+            // adjust if necessary
             wxWindow *parent = GetParent();
             if ( parent )
             {