Thermoplastic moulding compositions of the ABS type of I) at least one graft copolymer which is obtainable by emulsion polymerization of styrene and acrylonitrile in the weight ratio 90:10 to 50:50, wherein styrene and/or acrylonitrile can be completely or partly replaced by .alpha.-methylstyrene, methyl methacrylate or N-phenylmaleimide, in the presence of at least two butadiene polymer latices of types (A) and (B), which each contain, copolymerized, 0 to 50 wt. % of a further vinyl monomer, and wherein the weight ratio of monomers used to butadiene polymers used is 25:75 to 70:30, and II) at least one copolymer of styrene and acrylonitrile in the weight ratio 90:10 to 50:50, wherein styrene and/or acrylonitrile can be completely or partly replaced by .alpha.-methylstyrene, methyl methacrylate or N-phenylmaleimide, characterized in that the butadiene polymer latex (A) has a particle diameter d.sub.50 .ltoreq.320 nm, a width of the particle size distribution (measured as d.sub.90 -d.sub.10 from the integral particle size distribution) of 30 to 100 nm, and a gel content.ltoreq.70 wt. % and the butadiene polymer latex (B) has a particle diameter d.sub.50 .gtoreq.370 nm, a width of the particle size distribution (measured as d.sub.90 -d.sub.10 from the integral particle size distribution) of 50 to 500 nm and a gel content.gtoreq.70 wt. %.