Fibro-osseous lesions represent a variety of bone proliferations each characterized by different morphologic patterns of osteoid production. Psammomatoid ossifying fibroma (POF) is characterized histologically by numerous small round ossicles resembling psammoma bodies and is a locally invasive lesion of facial and cranial bones. Two cases of POF arising in the ethmoid sinus and involving the orbit are presented to emphasize the importance of complete surgical removal of involved bones. Histologically, portions of POF may demonstrate other patterns of osteoid production, which resemble fibrous dysplasia and Paget's disease of bone. The variation in radiodensity in POF on computed tomography is a function of the density of psammomatoid ossicles and of the coexistence of other "minor" forms of bone proliferation.