The invention relates to polymer blends of a styrene copolymer A selected from the group consisting of styrene acrylonitrile copolymers (SAN), styrene acrylonitrile maleic anhydride terpolymers (SMA), styrene acrylic copolymers, acrylonitrile butadiene styrene terpolymers (ABS), acrylonitrile butadiene styrene terpolymers with polyamide (ABS/PA), and acrylonitrile styrene acrylate terpolymers (ASA); and at least one copolymer B selected from the group consisting of styrene-butadiene block copolymers (SBC) and styrene-isoprene block copolymers (SIS); wherein the mold shrinkage of the polymer blend is reduced by at least 5% compared to the mold shrinkage of the pure styrene copolymer A.A process for the preparation of the polymer blends and the uses of the polymer blends in an injection molding process are described.