Use attached to reproduce. Workaround: AddHandler RadDropDownList2.DropDownListElement.AutoCompleteSuggest.DropDownList.PopupOpening, AddressOf RadDropDownList2_PopupOpening RadDropDownList2.DropDownListElement.AutoCompleteSuggest.DropDownList.MaxDropDownItems = 10 Private Sub RadDropDownList2_PopupOpening(sender As Object, e As System.ComponentModel.CancelEventArgs) Dim args = DirectCast(e, RadPopupOpeningEventArgs) Dim ownerElement = (TryCast(sender, RadDropDownListElement)) Dim loc = ownerElement.ElementTree.Control.PointToScreen(ownerElement.ControlBoundingRectangle.Location) args.CustomLocation = New Point(loc.X, loc.Y + RadDropDownList2.Height) End Sub