I read through the manpage on the TList widget, and learned the following:

• In order to know how to correctly extract content from the (set of) selected item(s), you have to know what sort of data they contain -- that is, what sort of data you put into the selected item(s): image, text, or "imagetext".
• The only features that set TList apart from a common, simple Listbox are: (1) the ability to assign distinct colors to individual list items (all items in a Listbox use the same colors), and (2) the ability to have items shown in a grid, with the indexing ordered horizontally or vertically (Listbox only displays a single-column vertical list).

If you don't happen to be using either of those two special features, then you might as well stick with using a plain old Listbox -- it's easier. If you do need those features, then Podmaster's sub-reply, together with your own knowledge about how you are putting items into the TList, should lead you to the answer.