A panoramic radiograph of a 27-year-old female who had sustained midfacial trauma incidentally revealed a greatly expanded, hyperlucent right maxillary sinus. Further radiological exploration, including tomography, demonstrated that the expansion was mainly localized to the inferomedial part of the antrum with encroachment on the nasal and oral cavities. ENT examination was unremarkable. The lesion was diagnosed as a pneumocele. No treatment was rendered. Repeated tomography nine years later showed no changes. Today, 23 years later, the patient is still asymptomatic. A literature review reveals only nine previous cases of pneumocele of the maxillary sinus.