Fibrous dysplasia (FD) is a developmental tumor like condition that is characterized by replacement of normal bone by an excessive proliferation of cellular fibrous connective tissue intermixed with irregular bony trabeculae. Central giant cell granuloma (CGCG) is described as a benign lesion affecting the mandible and maxilla that consists of a massive fibrohistiocytic proliferation with numerous heavily hemosiderin-laden multinucleate-giant cells. A 20 year old woman present at the Department of Oral Medicine, Dentistry School, Tehran University of Medical Sciences with a slowly growing non painful swelling of the right mandible for one year. Our differential diagnosis was osteoma, osteoid osteoma and Fd. The histological feature reveal Central giant cell granuloma fibrous dysplasia. Central giant cell granuloma and fibrous dysplasia occurring in the same jaw is rarely reported in the literatures.