The present invention relates to novel radiation-curing powder coating binders containing maleic and/or fumaric acid esters and one or more amorphous or partially crystalline resins containing at least one group that reacts with ethylenically unsaturated compounds under the action of actinic radiation to form a polymer. The binders have a glass transition temperature ranging from 30 to 90.degree. C. The binders can be used as a constituent in coating compositions.