Red blood cells labeled with technetium Tc 99m were used to evaluate the vascular nature of a subcutaneous tumor in a 12-year-old girl. The low perfusion and high blood pool that characterized the lesion were considered highly suggestive of subcutaneous cavernous hemangioma. This noninvasive method for diagnosing soft tissue hemangiomas is more specific than other imaging modalities such as ultrasound and arteriography. The usefulness and the importance of the method prior to surgical biopsy or resection are discussed.