AbstractMucoceles involving the sphenoidal sinus are not as common as those affecting the frontal and ethmoidal sinuses. The subtle expansile change produced by a sphenoidal sinus mucocele often requires conventional tomography or computed tomography examination to be detected. Similarly, involvement of surrounding structures by a sphenoidal mucocele may require special study, which this section illustrates. The sphenoidal enlargement and density change produced by fibrous dysplasia may mimic sinus disease. Focal or widespread bone destruction resulting from neoplastic involvement of the sphenoidal sinus requires special examination similar to that used with mucoceles.