The supermolecular structures formed in a block copolymer-solvent system were considered by using the scaling method. The equilibrium characteristics of the superstructures of different morphologies formed by two-block copolymers with non-crystallizable blocks were determined as a function of the molecular weight and composition of copolymer and the strength and concentration of the solvent in the system. The composition-concentration diagram of the system was obtained. The lamellar superstructure formed by a block copolymer with one crystallizable block was analysed. The results of the theory were compared with the experimental data.