We report a five-year-old girl with a sinonasal cementoossifying fibroma with CT findings that reveal the invasion of all paranasal sinuses and the remodeling of facial bones. It was possibly a congenital lesion and caused a slowly progressive nasal obstruction and anosmia. Tumor removal with transnasal endoscopic approach was applied and total removal of the mass was accomplished. It was found out to be the cementoossifying fibroma of the paranasal sinuses when the results of the pathological examinations were obtained. (C) 2003 published by Elsevier Ireland Ltd.