The present invention relates to a method for painting non-polar, in particular polyolefin plastic substrates, comprising the steps: 1. applying a pigmented paint layer consisting of a colour- and/or effect-imparting coating composition directly to the plastic substrate and 2. curing the pigmented paint layer thus obtained, wherein the applied colour- and/or effect-imparting coating composition comprises A) 30 to 90% by weight of a conventional colour- and/or effect-imparting coating composition constitution, containing Aa) at least one binder, Ab) at least one colour and/or effect pigment, Ac) at least one organic solvent and/or water and Ad) optionally, conventional paint additives and B) 10 to 70% by weight of an adhesion-promoting constitution, containing Ba) at least one ethylene vinyl acetate copolymer, Bb) at least one chlorinated rubber, Bc) at least one chlorinated polyolefin and Bd) optionally, organic solvents and/or water and conventional paint additives, wherein the sum of the portions of components A) and B) makes up 100% by weight.