Our data highlight the important role played by genetic background and ripening stage in determining the antioxidant potential of watermelon. The amount of lycopene and b-carotene, as well as the LAA, markedly increased in all the studied watermelon cultivars with ripening, whereas the contents of total phenols, flavonoids, total vitamin C and HAA were affected by fruit ripening in a cultivar-dependent way. Hence, the increase of antioxidants during watermelon fruit ripening must not be generalized; rather, their contents reach levels leading to the maximum nutritional quality depending on their genotypic differences.