Osteomas of the paranasal sinuses are benign, often asymptomatic, tumors which progress very slowly. Endocranial development of an osteoma can breach the dura mata, allowing air to enter the cranium producing pneumocephalia which leads to severe neurological deficiencies. Pneumocephalia is an exceptional complication of osteoma. We found 40 cases reported in the literature. Brain CT scan easily gives the diagnosis. Surgical exeresis with closure of the breach gave very satisfactory results in our 2 cases.