The clinical diagnosis of synovial tumors and tumorlike lesions is difficult, and radiographic findings may establish a confident diagnosis only in some cases. MR imaging has become the modality of choice in evaluating these lesions, because with it a presumptive diagnosis can be made in most cases. Our goal is to review the MR features of pigmented villonodular synovitis, giant-cell tumor of the tendon sheath, synovial chondromatosis, synovial hemangioma, lipoma arborescens, synovial cysts and synovial sarcoma, emphasizing those findings that suggest a specific diagnosis.