Thank you for contacting us.
You can achieve that by editing the style of the ComboBox. The easiest way to do that is to drop a RadComboBox in the Blend Expression design surface and right-click it, choose from the menu Edit Template->Edit a Copy.
Then in the NonEditableComboBox
ControlTemplates add a Grid with some columns and TextBlocks in it. This will play the role of the header. After that edit the Item's DataTemplate to look like this Grid.
Attached you will find a sample project in which that is illustrated.
If you have further questions please feel free to contact us again.
the Telerik team
Do you want to have your say when we set our development plans? Do you want to know when a feature you care about is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items.