Objective: Fibrous dysplasia (FD) and ossifying fibroma (OF) show similar histological and radiological features, making distinction between them a diagnostic dilemma requiring clarification. Study Design: Forty(20 FD, 20 OF) paraffin-embedded specimens were immunohistochemically stained using the primary antibody Osteocalcin (OC). The immunostained area fraction was evaluated in the bone trabeculae alone and in both the bone trabeculae and the connective tissue stroma together. Results: All cases of FD and OF demonstrated OC immunostaining in both the bone trabeculae and the stromal cells. In FD, osteocalcin was more expressed in stromal cells, while in OF, immunoreactivity was more marked in bone trabeculae. The area fraction expressing OC in both the bone tarbeculae and fibrous stroma was significantly higher in FD than OF (p= 0.025). Conclusion: The stromal spindle-shaped cells in FD are of the osteoblastic lineage. Osteocalcin expression can be a significant support in differential diagnosis of FD and OF.