To reproduce: var stackPanel = new StackLayoutElement { Orientation = Orientation.Vertical }; stackPanel.Children.Add(new TextPrimitive { Text = "Demo" }); stackPanel.Children.Add(new TextPrimitive { Text = "Demo" }); Panel.PanelElement.Children.Add(stackPanel); Panel.AutoSize = true; // <= false works fine Workaund: - Put the panel in a control: public class MyControl : RadControl { protected override void CreateChildItems(RadElement parent) { base.CreateChildItems(parent); var stackPanel = new StackLayoutElement { Orientation = Orientation.Vertical }; stackPanel.Children.Add(new TextPrimitive { Text = "Demo" }); stackPanel.Children.Add(new TextPrimitive { Text = "Demo" }); parent.Children.Add(stackPanel); } protected override RootRadElement CreateRootElement() { RootRadElement root = base.CreateRootElement(); root.BackColor = Color.Transparent; return root; } }