Fibrous dysplasia is a rare benign condition of unknown etiology. The term was introduced by Lichtenstein 1938. In this disease, normal bone structure is replaced by fibrous connective tissue with trabeculae bone. The disease can involve any bone in the body and can be monostotic or, less frequently, polyostotic. Present the case of a male patient, 55 years with complaints of hearing loss on the right for three years and a history of tympanoplasty for 20 years in the same ear. Otoscopy shows narrowing of external auditory canal to the right tympanic membrane intact. Computed tomography is the examination of choice for study of injury, assessment of the extent and surgical preparation. In our case, the topographic images were taken from a standard hyperdense lesion of the temporal bone, with an area of sclerosis characteristic. We ordered nuclear magnetic resonance showing thickening and bone material with a iso signal on T1 and hypersignal T2, occupying the mastoid cells.