The present invention relates to a dispersion of polymer particles, in a liq. medium, the particles having a soft polymeric core and being surface-stabilized by a stabilizing block copolymer comprising at least one block that is sol. in the liq. medium and at least one block that is insol. in the medium. The invention also relates to a cosmetic compn. comprising the dispersion, and also to a treatment method using the compn. A dispersion was prepd. from poly(Me acrylate) in isododecane stabilized by 2-ethylhexyl acrylate-Me acrylate triblock copolymer. A lipstick was prepd. from the above dispersion 13, polyethylene wax 3, and isododecane qs to 100%.