The invention relates to a dispersion of polymer particles in a liquid carbon-based medium, wherein said polymer is chosen from at least one block copolymer comprising at least one first block that is soluble in said liquid carbon-based medium and at least one second block that is insoluble in said liquid carbon-based medium. Also disclosed herein is a cosmetic composition comprising, in a cosmetically acceptable medium, said dispersion, and further disclosed is a cosmetic process for making up, cleansing, protecting against the sun, shaping, dyeing or caring for keratin materials, for example, body or facial skin, the nails, the hair and/or the eyelashes, using this composition.