A thermoplastic molding composition having improved mechanical properties is disclosed. The composition contains (A) aromatic polycarbonate and/or polyester carbonate (B) at least one graft rubber, obtained by emulsion polymerization of styrene and acrylonitrile in the presence of at least two rubber latices of type (B1) and (B2) where (B1) has a particle diameter d50 of ≦350 nm, a particle size distribution range of 30 nm to 100 nm, and a gel content of 70 wt. %, and (B2) has a particle diameter of ≧350 nm, a particle size distribution range of 50 nm to 500 nm, and a gel content of ≧70 wt. %, and the difference in the average particle diameter of B1 and B2 is ≧50 nm, (C) an optional copolymer of styrene and or acrylonitrile and for methyl methacrylate and/or N-substituted maleinimide, and optionally (D) flame retardant as well as optionally conventional additives.