in the toolbox there are two buttons side by side on the 3rd set of buttons from down up it says edit in quick mask or standard. I only use the quick mask for subtle approaches of masking (feathered) it can be applied with a brush for the quickmask (when the work area bcomes red) in standard you have to use the marquee buttons. (that's what I use...sounds awfully hard..it works for me,anyway)