You can either buy a deodorized product or add your own deodorizer to plain litter, however some deodorized litters contain chemicals and fragrances that repel cats, forcing them to use other places in the house. It's often easier on the pet and on the pocketbook to buy plain clay litter and add your own odor counteractant. Most experienced cat owners favor plain old baking soda, 85% cat owners indicated that they had better results with baking soda than any other chemical treatments of any other kind. Mix one part baking soda to three parts litter, and always put a layer of soda on the very bottom of the box. Also don't forget always keeping the box clean is the great odor-conquering secret.