Osteomas are uncommon benign turners, occasionally located in the paranasal sinuses, of which the frontal and ethmoid sinus is the most frequent site. The etiology of the osteoma is still unknown but three possible theories have been proposed; embryological, traumatic and infective. The most common symptoms of osteoma are facial pain and headache, but most of them are asymptomatic and discovered incidentally on routine sinus radiography. Recently, the authors experienced two cases of large osteoma of the ethmoid sinus that were removed successfully by external ethmoidectomy.