Abstract: An impact resistance thermoplastic molding composition contains, each percentage being based on A+B, from 80 to 55% by weight of a hard matrix A of a copolymer containing at least 95% by weight of an aromatic vinyl monomer a.sub.11 of from 8 to 10 carbon atoms and at least one comonomer a.sub.12 in a proportion of 0.1 to 5% by weight, based on A, and from 45 to 20% by weight of a soft phase B which, uniformly dispersed in the hard matrix, has an average particle diameter d.sub.50 (volume average) of from 3.5 to 9 .mu.m and is obtainable by polymerization of the mixture of monomers a.sub.11 and a.sub.12 in the presence of an elastomer (rubber) and subsequent isolation of the useful product, wherein the comonomer a.sub.12 has the general formula I ##STR1## where X is --OR.sup.2, --COOR.sup.2 or --CONHR.sup.3,R.sup.1 is hydrogen or methyl andR.sup.2 and R.sup.3 are each alkyl of from 1 or 2 to 10 carbon atoms with at least one OH or epoxy group or at least one other polar group.