The present invention relates to a dispersion of polymer particles in a liquid carbon-based medium, the said particles having a flexible polymeric core and being surface-stabilized with a block stabilizing polymer comprising at least one block that is soluble in the said carbon-based medium and at least one block that is insoluble in the said carbon-based medium.The invention also relates to a cosmetic composition comprising the said dispersion, and to a cosmetic treatment process using the said composition.