The micellization thermodynamics, micelle structural parameters, and micelle size distribution for polystyrene-b-poly(ethylene/butylene)-b-polystyrene copolymer solutions in 4-methyl-2-pentanone were studied. The solvent used is selective for the outer PS blocks of the copolymer. Standard Gibbs energy, standard enthalpy, and standard entropy of micellization were determined from Light scattering measurements. The influence of the copolymer. molar mass on these magnitudes was analyzed. The structural parameters of micelles formed by different triblock copolymers were determined by static light scattering. Micelle molar mass and size increase with the length of the copolymer chain for a constant copolymer composition; however the association number decreases. Micelle size distribution functions were obtained from dynamic light scattering and size exclusion chromatography measurements. The results obtained by means of both techniques were compared.