Hallabong is a representative and popular citrus fruit in Jeju Island. It is a hybrid fruit from Japan in early 1970’s and it had many different names such as Dekopon and Hallabong. Since the 1990’s , the name was united to Hallabong in Korea because its characteristic bump looks like the top of Halla Mountain. Hallabong and C. junos are best in harmony when it is made as a marmalade like syrup and stirred with hot water to drink. Total polyphenol and total flavonoid contents of Hallabong fruit are the highest among Yuja and orange in medium polar fraction, which is naturally related to anti-oxidant activity.