Osteoma of the paranasal sinus is relatively rare, but is the most common one among the benign tumor of the paranasal sinuses. It is frequently seen in young aged male. And its pathogenesis is still questionable, however several theories were reported, such as developmental, traumatic and inflammatory etc. Recently the authors had experienced on case of large osteoma originated from right ethmoid sinus, which was removed successfully through external ethmoidectomy combined with lateral rhinotomy approach. Postoperative result was good. Related articles were reviewed, and discussions were made.