An aqueous cosmetic hair-setting composition consisting of an aqueous dispersion of: (a) particles of a film-forming polymer having carboxylic acid functions neutralized at a rate of 10-80 % by a non-volatile monobasic agent, said particles having an average diameter of 10-300 nm; and (b) at least one plasticizer. The composition is preferably an aerosol spray, a setting lotion or a styling foam.
