Telerik RadComboBox is a very flexible control and with all the advanced features it represents, it is definitely a control to go with in your ASP.NET applications.
RadComboBox for ASP.NET AJAX supports templates, both server and client templates; the latest will be introduced in the release coming next week. Having into consideration the templates, you are able to build up an item representation that will suit your needs best. Please find more information on this matter on our online demos: RadComboBox Templates
as well as on our online documentation: RadComboBox Templates Overview
The following online demo might be of help too for it represents an interesting approach to 'Related RadComboBoxes' scenario: http://demos.telerik.com/aspnet-ajax/combobox/examples/functionality/multiplecomboboxes/defaultcs.aspx
I encourage you to take a look at the online demos of RadTreeView as well, so you would be able to choose a RadTreeView representation which will suit your needs best as a RadComboBoxItem template: RadTreeView Online Demos
I hope this will help.
the Telerik team
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