A high impact strength thermoplastic composition comprising: a) from 10 to 90% by weight of a rubber-modified monovinylidene aromatic (co)polymer; b) from 10 to 90% by weight of a polyphenylene ether; wherein: said rubber-modified monovinylidene aromatic (co)polymer a) comprising: I) a matrix comprising monovinylidene aromatic polymer, and II) from 5 to 25% by weight of rubber in the form of discrete rubber particles dispersed within the matrix, wherein the rubber particles comprise a blend of at least two polybutadienes as well as graft- and block copolymers of polybutadiene and monovinylidene aromatic polymer segments, said rubber particles exhibit: - an average particle size by volume comprised between 0.8 and 5.5 μm, measured by laser light scattering; said blend of at least two polybutadienes comprises: - at least 50 % by weight of one or more polybutadiene(s) with a cis-1,4 structure content of at least 80% by weight and - at most 50% by weight of one or more polybutadiene(s) with a trans-1-4 structure content of at least 25% by weight and a 1,2-vinyl content of at least 5% by weight; said blend of at least two polybutadienes, as such and prior to being part of the rubber-modified monovinylidene aromatic (co)polymer a), being characterized by a dynamic solution viscosity, at 20 °C, comprised between 50 and 160 mPa.s, as determined by Brookfield viscometer according to ISO 2555 at a concentration of 5.43% by weight in toluene; and said polyphenylene ether b) has a repeating structural formula: wherein R1 and R2 are independently selected from the group consisting of a hydrogen atom, a halogen atom, C1-4 alkyl radicals, C1-4 alkoxy radicals, C6-10 aromatic radicals which are unsubstituted or substituted by a C1-4 alkyl radical, halohydrocarbon radicals having at least two carbon atoms between the halogen atom and the phenyl nucleus, hydrocarbonoxy radicals and halohydrocarbonoxy radicals having at least two carbon atoms between the halogen and the phenyl nucleus, and wherein n is an integer of at least 50. a) from 10 to 90% by weight of a rubber-modified monovinylidene aromatic (co)polymer; b) from 10 to 90% by weight of a polyphenylene ether; said rubber-modified monovinylidene aromatic (co)polymer a) comprising: I) a matrix comprising monovinylidene aromatic polymer, and II) from 5 to 25% by weight of rubber in the form of discrete rubber particles dispersed within the matrix, wherein the rubber particles comprise a blend of at least two polybutadienes as well as graft- and block copolymers of polybutadiene and monovinylidene aromatic polymer segments, said rubber particles exhibit: - an average particle size by volume comprised between 0.8 and 5.5 μm, measured by laser light scattering; said blend of at least two polybutadienes comprises: - at least 50 % by weight of one or more polybutadiene(s) with a cis-1,4 structure content of at least 80% by weight and - at most 50% by weight of one or more polybutadiene(s) with a trans-1-4 structure content of at least 25% by weight and a 1,2-vinyl content of at least 5% by weight; said blend of at least two polybutadienes, as such and prior to being part of the rubber-modified monovinylidene aromatic (co)polymer a), being characterized by a dynamic solution viscosity, at 20 °C, comprised between 50 and 160 mPa.s, as determined by Brookfield viscometer according to ISO 2555 at a concentration of 5.43% by weight in toluene; and I) a matrix comprising monovinylidene aromatic polymer, and II) from 5 to 25% by weight of rubber in the form of discrete rubber particles dispersed within the matrix, wherein the rubber particles comprise a blend of at least two polybutadienes as well as graft- and block copolymers of polybutadiene and monovinylidene aromatic polymer segments, said rubber particles exhibit: - an average particle size by volume comprised between 0.8 and 5.5 μm, measured by laser light scattering; - an average particle size by volume comprised between 0.8 and 5.5 μm, measured by laser light scattering; said blend of at least two polybutadienes comprises: - at least 50 % by weight of one or more polybutadiene(s) with a cis-1,4 structure content of at least 80% by weight and - at most 50% by weight of one or more polybutadiene(s) with a trans-1-4 structure content of at least 25% by weight and a 1,2-vinyl content of at least 5% by weight; - at least 50 % by weight of one or more polybutadiene(s) with a cis-1,4 structure content of at least 80% by weight and - at most 50% by weight of one or more polybutadiene(s) with a trans-1-4 structure content of at least 25% by weight and a 1,2-vinyl content of at least 5% by weight; said blend of at least two polybutadienes, as such and prior to being part of the rubber-modified monovinylidene aromatic (co)polymer a), being characterized by a dynamic solution viscosity, at 20 °C, comprised between 50 and 160 mPa.s, as determined by Brookfield viscometer according to ISO 2555 at a concentration of 5.43% by weight in toluene; and said polyphenylene ether b) has a repeating structural formula: wherein R1 and R2 are independently selected from the group consisting of a hydrogen atom, a halogen atom, C1-4 alkyl radicals, C1-4 alkoxy radicals, C6-10 aromatic radicals which are unsubstituted or substituted by a C1-4 alkyl radical, halohydrocarbon radicals having at least two carbon atoms between the halogen atom and the phenyl nucleus, hydrocarbonoxy radicals and halohydrocarbonoxy radicals having at least two carbon atoms between the halogen and the phenyl nucleus, and wherein n is an integer of at least 50.