Osteoma is the most common benign tumor originating in the paranasal sinuses, and the frontal sinus is the most frequent site. Osteoma may occur at any age but the most frequent incidence is the third decade and it is histologically classified as eburnated, compact, cancellous and mixed type. Recently, the authors saw a patient with exophthalmos and downward displacement of left eyeball due to a huge osteoma in the frontal sinus. We removed the osteoma by osteoplastic operation of the frontal sinus and the removed defect was implanted with adipose tissue from the patient’s own left abdomen. We report this case with review of the literature.