The oil obtained by distillation of the liquid of the screw-pressed residues of the cold-extraction of mandarin oil, and the cold-pressed mandarin oil have been examined using capillary GC. Thirty-six components were characterized in both oils. The results of 266 analyses of cold-pressed mandarin oil, 29 analyses of distilled mandarin oil and 26 analyses of mixtures of 5–20% of distilled oil mixed with cold-pressed oil are presented. Component ratios of terpinen-4-ol with cis-sabinene hydrate, trans-sabinene hydrate, citronellal and decanal have been used to detect the additions of the less valued distilled oil in the cold-pressed oil. In most cases the component ratios found in mixtures of 10% distilled oil in cold-pressed oil can be used to infer that such a mixture has taken place. Nevertheless, because of wide component value ranges found in both the cold-pressed and distilled oils it remains difficult to determine the lower limits of adulteration detection.