The present invention relates to a process for the production of olefinically unsaturated polyester resins containing at least 0.025 moles of urethane groups per 100 g of resin by reactingA) olefinically unsaturated polyester resins which contain alcoholic hydroxyl groups, have a molecular weight (M.sub.n) of 800 to 10,000, an acid vlaue of 0 to 50 and a hydroxyl number of 30 to 120, and are based on the reaction product ofI) a dicarboxylic acid component containing a) 90 to 100 mole percent of maleic acid, maleic anhydride and/or fumaric acid and b) 0 to 10 mole percent of another carboxylic acid andII) 1.1 to 1.5 moles, based on one mole of the dicarboxylic acid component, of a polyol component containing c) 0.1 to 0.5 moles of at least one saturated cycloaliphatic diol having 6 to 18 carbon atoms, d) 0.5 to 0.9 moles of at least one saturated aliphatic diol having 2 to 6 carbon atoms and e) 0.1 to 0.5 moles of at least one .beta.,.gamma.-ethylenically unsaturated ether alcohol having 5 to 14 carbon atoms, withB) an organic polyisocyanate baased on a member selected from the group of biuret-, isocyanurate-, uretdione- and urethane-modified polyisocyanates having 8 to 30% by weight of (cyclo)-aliphatically bound isocyanate groups in an amount sufficient to provide a ratio of isocyanate groups of component B) to hydroxyl groups of component A) of 0.1:1 to 1:1.The present invention also relates to the olefinically unsaturated polyester resins containing urethane groups obtained by this process and to coatings prepared from coating compositions based on these olefinically unsaturated polyester resins and cured by free radical polymerization.