The invention relates to thermosetting powder paint compositions based on carboxyl group-containing polyester resins as well as polyepoxides and/or ß-hydroxyalkylamides serving as curing agents. The polyester resins have an acid number ranging from 10 to 100 and a hydroxyl number no greater than 15 mg KOH/g polyester resin and comprise at least 50 mol %, with regard to all of the contained dicarboxylic acids, of units of isophthalic acid and up to at least 50 mol %, with regard to all of the contained diols, of units of neopentyl glycol and contain no more than 10 mol %, with regard to all of the dicarboxylic acids and diols, of monomers having a functionality of 3 or higher. By adding 0.05 to 5 % by weight of a heterocyclic polycarboxylic acid to the powder paint raw batch, preferably by melting this acid into the polyester resin used for producing the powder paint after the powder paint is produced, it is possible to obtain highly weather-proof powder coatings having an excellent mechanical level and surface aspect.