The chemical composition of the cold-pressed oils obtained from three mandarin cultivars (“Comun,” “Malvasio” and “Ellendale”) and two mandarin hybrids (“Ortanique” and “Malaquina”) grown in Uruguay were examined using a combination of alumina column chromatography and capillary GC. Forty-five constituents were characterized in the oils with the limonene content varying from 75.26–96.23%. The composition and olfactory characteristics of these oils were compared with those of Italian mandarin oil and Uruguayan sweet orange oil. It was found that the “Ortanique” and “Ellendale” oils were very different from normal mandarin oil, with great similarity in composition and olfactory characteristics to sweet orange oil. The oil of “Malaquina” is also similar more to sweet orange oil than mandarin oil although it is quite rich in aliphatic aldehydes, particularly decanal. The oil of the cv. Malvasio has a composition which is between mandarin and sweet orange oils. The oil of cv. Comun is the only one found to possess olfactory and chemical characteristics similar to Italian mandarin oil.