Multiple select from a 2-levels category - how?

Question

Assumed I need to provide a way to select items from a 2-level hierarchy. The simplest way is to have a long list of sets of checkboxes (each with a name) - that's great for discovery of the variety of items, however scrolling multiple screens up and down is not the best UX in the world.

So which is the best way to:

• Display the hierarchy in a compact way yet to be able to discover the inner items quickly enough
• See the already selected items in one place and being able to deselect them

Answer 1

You could go for a drop down list for the parent category and a check list for items from that category. The limitation here is you can only select items under one parent category at a time. But if there is to much data then this might be a good option.