http://www.cozycatfurniture.com/cat_newsletters/cat_newsletter_2_issue.html

16.NEVER use scented litter. Perfumed, chemical scents repel cats. When you
wash the litter box, use hot water and a mild dishwashing liquid. Do not use
harsh chemicals that will leave a lingering odor.

that being posted everywhere on the net, my crew use scented litter (fresh
step - a very mild scent) and don't have a problem with it,  When I replace
the litter in one of their boxes, it is the box that is used most (as
opposed to the freshly scooped, clean litter box with litter that has been
out of the box for a couple of weeks)