Cementoossifying fibroma is a rare nonodontogenic tumor of the periodontal membrane that arises from the mesodermal germ layer. This nonneoplastic, locally destructive tumor has occurred as an osseous lesion in the mandible, the maxilla, the zygoma, all the paranasal sinuses, and the orbital and petromastoid regions. It has occurred as an extraosseous lesion in the gingiva and the auricle. The diagnosis requires correlating a variety of clinical, radiologic, and histologic factors. The recurrence rate is high, particularly for lesions in the paranasal sinuses. Surgical management via a local excision as wide as possible is suggested. We describe the case of a 32-year-old woman with an isolated cementoossifying fibroma of the right ethmoid bulla, and we review the diagnosis, differential diagnosis, and management of this tumor.