This is a report of a case of osteoma located in the ethmoid air cells which has been treated in our clinic. It was extened over the right ethmoid air cells and frontal sinus. The patient was a man of 27 years old. The tumor was walnut sized, whitish, compact, and has irregular surface. It was noted 5 years ago for the time, gradually increased the size and became hard mass at the right inner orbital ridge. The tumor was removed by external approach under the local anesthesia and the prognosis of the operation was good.