Comicellization of a diblock block copolymer polystyrene-block-hydrogenated polyisoprene, PS-HPI (M-w 1.05 x 10(5) g mol(-1), the weight fraction of styrene wps 0.34), and triblock copolymer polystyrene-block-hydrogenated polybutadiene-block-polystyrene, PS-HPB-PS (M-W 7.0 x 10(4) g mol(-1), W-PS 0.28), in selective solvents was investigated by static and dynamic light scattering methods at 25-70 degreesC. Decane was a selective solvent for HPI and HPB blocks and 1,4-dioxane for PS blocks. HPI and HPB blocks are incompatible. Only the diblock copolymer formed micelles in decane while the triblock was molecularly dissolved at low concentrations and the measurement temperatures. Both the copolymers formed micelles of different sizes in 1,4-dioxane solutions. Comicellization was observed at all weight fraction of PS-HPB-PS, X, in solutions of copolymer mixtures in both solvents. In contrast to mixtures of chemically identical diblock copolymers with different molecular weights of the constituent blocks in selective solvents, small changes of micellar parameters resulting from comicellization were found in the copolymer mixtures under study. This is due to different constitution of the copolymers and their partial incompatibility. The X dependence of the molecular weight and size of comicelles in decane at low values of X was successfully described by adsorption of the PS-HPB-PS copolymers on micelles of the PS-HPI copolymer. The large PS-HPI copolymers were accommodated in small micelles of the PS-HPB-PS copolymer in 1,4-dioxane solutions with an excess of the PS-HPI.