ABSTRACT. Mandarins are characterized, among the Citrus genus, by a large diversity of species and varieties. Genetic evidences indicate that mandarin is one of the ancestral Citrus species, originated from Asiatic regions, and also an ancient parental of orange. This genetic diversity originates the nutritional and nutraceutical properties of mandarin fruits to vary largely among the different species and varieties. Sugars, acids, carotenoids, polyphenols (flavonoids and phenolic acids), limonoids, and vitamins are the most relevant components in mandarin flesh that collectively determine the mandarin flavor as a whole. Mandarin fruits are particularly rich in β-cryptoxanthin, a xanthophyll with provitamin A activity and important health-related properties. Volatile compounds also exert a predominant effect on consumers' acceptance and therefore, represent a relevant quality trait in this crop. A comparison of the main nutritional constituents in fruits of the different mandarin species and varieties in the world is described and discussed. Copyright © 2016 Elsevier Inc. All rights reserved.