To reproduce: 1. Add a RadMenu with one item which has one child item. 2. Click on "radMenuItem1" then will appear "radMenuItem2 " . - Keep ("radMenuItem2") open and do not click on it - 3. Go out of the form and click on empty area . 4. Return to the menu and just move mouse over the "radMenuItem1" and it will appear "radMenuItem2" and also move the mouse over the "radMenuItem2" and keep it open . ("do not click on menus") 5. Go out of the form and click the Show Desktop button on the bottom right of the screen 6. Now you can see the problem , the menu has not closed Workaround: override the WndProc method in your Form with the following: protected override void WndProc(ref Message m) { if (m.Msg == NativeMethods.WM_SIZE && (int)m.LParam == 0 && (int)m.WParam == 1) { PopupManager.Default.CloseAll(RadPopupCloseReason.AppFocusChange); } base.WndProc(ref m); } if the above does not work, you can try the following: private void Form1_Deactivate(object sender, EventArgs e) { PopupManager.Default.CloseAll(RadPopupCloseReason.AppFocusChange); }