There are different kinds of list boxes with the following additional navigation conventions:
Drop-down list boxes by default show only the selected item. A small button to the right of the control shows a downward-pointing arrow. Select the arrow to display more items from the list box. If there are more choices than can fit in the preset list box area, a slider appears along the side of the list box. Show or hide the list using ALT+DOWN ARROW, ALT+UP ARROW, or F4. The TAB key selects an item.
Extended selection list boxes support selecting single items, blocks of items, or combinations of the two. After selecting an item, hold down CTRL+navigation keys to select or clear additional items or blocks of items.