[ $eta-Cryptoxanthin$ ] content was determined in Shiranuhi mandarin fruits harvested at monthly intervals from October to February in Jeju Island. Crude carotenoids were extracted from both peel and flesh of Shiranuhi mandarin fruits and analyzed using TLC and HPLC; $eta-cryptoxanthin$ was indicated the Rr value of 3.2 and retention time of 23 min, respectively. $eta-Cryptoxanthin$ contents in both peel and flesh were increased gradually as the citrus fruits ripened fully until harvesting season (February). According to the harvesting time, $eta-cryptoxanthin$ contents in the peel were $0.15;mg\%;(October),;0.28;mg\%;(November),;0.38;mg\%;(December),;1.23;mg\%;(January),;and;1.71;mg\%;(February).$In the flesh, $eta-cryptoxanthin$ contents were lower than those of peels, having $0.06;mg\%;(October),;0.08;mg\%;(November),;0.19;mg\%;(December),;0.26;mg\%;(January),;and;0.65;mg\%;(February).$ These results demonstrate that $eta-cryptoxanthin$ in Shiranuhi mandarin fruits accumulated during ripening of the citrus fruits. In particular, the peels had much higher concentrations of $eta-cryptoxanthin$ and have potential for use as a functional ingredient.