A thermoplastic molding composition containing 1 to 99 parts by weight of aromatic polycarbonate or polyester carbonate and 1 to 99 parts by weight of at least one graft polymer prepared by solution polymerization is disclosed. The graft polymer is characterized in having rubber content of 20 to 50 wt. % and in that the average particle size of its rubber phase is 80 to 600 nm. The composition, which optionally contains additives, flameproofing agents and reinforcing agents, is characterized by its improved mechanical properties.