The invention relates to novel cosmetic or dermatological compositions, characterized in that they comprise, in a cosmetically acceptable support, at least one solution or one emulsion of at least one multiblock polycondensate whose chain consists of the repetition of at least one polysiloxane block and of at least one polyurethane and/or polyurea block; the said polyurethane and/or polyurea block also including ionizable groups and the said polycondensate being dissolved in an aqueous, organic or aqueous-organic solvent system.These compositions may be used in particular in the cosmetic field of hair care, make-up or skincare.