Positron emission tomography (PET) with 2-[F-18]-Fluoro-2-deoxy-D-glucose (FDG) was performed in ninteen patients who had benign musculoskeletal tumors in order to determine if there was a relationship between histologic grade of tumor and FDG uptake of tumor. These patients had been evaluated previously with computed tomography (CT) or magnetic resonance (MR) imaging or both. The diagnoses were confirmed with incisional or excisional biopsy or by radiographic follow-up. Generally high-grade tumors had significantly greater uptake of FDG than low-grade lesions . Benign lesions such as giant cell tumor, fibrous dysplasia, and osteofibrous dysplasia showed significant elevation of SUV (Standardized Uptake Value) above 4.0. On the contrary. The current studies suggest the utility of FDG-PET imaging as an adjunct to CT or MR imaging in the evaluation of benign tumors. And results of PET suggest benign tumors with high SUV are histologically active lesion and tend to be locally aggressive.