Abstract: The invention relates to a composition comprising a) at least one polyolefin or vinyl polymer; b) at least one di- or poly-functional (co)polymer or (co)oligomer having a glass transition temperature of less than 10° C., wherein the functional group is a carbon-carbon double bond, an epoxy group, an amine group, a carboxylic acid group, a carboxylic acid ester group or a carboxylic anhydride group, an OH group, an SH group or an isocyanate group, and c) a multifunctional epoxide, which is different from the di- or poly-functional (co)polymer or (co)oligomer wherein the functional group is an epoxy group. The invention also relates to a method of improving the mechanical properties of polyolefins and to the polyolefin plastics articles produced thereby and to the use of di- or poly-functional (co)polymers or (co)oligomers having a glass transition temperature of less than 10° C. together with a multifunctional epoxy compound in improving the mechanical properties of polyolefins.