The dentinoma may be defined as an odontogenic tumor composed of dentine, connective tissue and occasionally of Odontogenic epithelium. The author has experienced a case of dentinoma developed in right maxillary sinus of a 32-year-old Korean female who was admitted to Department of Seoul National University Hospital on July, 22, 1974. She complained of slowly increasing mass at right cheek for the past 9 years. She had been operated as a odontogenic fibroma with comlete exicision. Pathologic study revealed as a typical dentinoma of right maxillary sinus. Postoperative course was uneventful.