The cemento-ossifying fibroma is probably the most frequent fibro-osseous lesion seen by oral pathologists. Occasionally, reports of lesions behaving in an aggressive fashion appear in the literature. At the present time, the relationship if these "aggressive" lesions to the "usual" fibromas is unclear. Two cases of "aggressive" cemento-ossifying fibroma are reported. Certainly, clinical, radiological, and histological characteristics of aggressive and usual fibromas do coincide. There are, however, diverging features warranting separation of different forms. These mild differences may be detected during preoperative assessment of the lesion, allowing a diagnosis of aggressive form to be made.