A cosmetic composition containing, in a cosmetically acceptable medium, at least one antidandruff agent and at least one amphoteric polymer containing at least one monomeric unit chosen from (meth)acrylate and (meth)acrylamide types containing at least one fatty chain, the fatty chain containing from 8 to 30 carbon atoms. This combination makes it possible to improve the deposition of the antidandruff agent. These compositions are used for washing and/or conditioning keratin substances such as the hair or the skin.