To determine the value and diagnostic accuracy of planar and SPECT Tc-99m-labeled red blood cell (Tc-99m RBC) scintigraphy in the investigation of suspected hepatic cavernous hemangioma as found on ultrasound. One hundred patients, 89 women (89%) and 11 men (11%), between 22 and 67 years old (mean age, 38 years) were evaluated for liver masses found on abdominal ultrasound. All the patients had previous Tc-99m RBC scintigraphy. The size of the lesions ranged from 1 to 9 cm. The final diagnosis was reached through cytologic biopsy, or histopathologic tests (or all of these). One hundred thirty lesions were found. With regard to the distribution of the lesions, 116 (89%) were single; 14 (3%) were multiple, with 118 (91%) in the right lobe and 12 (9%) in the left lobe; 83 (64%) were posterior; and 47 (36%) were anterior. With respect to the pattern of radioactivity fill-in, 86 (66%) lesions were typical and 44 (34%) were atypical. The results of Tc-99m RBC scintigraphy showed sensitivity, specificity, and positive and negative predictive and accuracy values of 97%, 83%, 98%, 77%, and 96% respectively. The use of SPECT improved the sensitivity value by 11% for lesions of 1 to 2 cm. Tc-99m RBC scintigraphy is the noninvasive technique most helpful in the diagnosis of hepatic hemangioma, especially in those at risk for lesion rupture or bleeding. SPECT should be performed whenever planar imaging fails to show the lesion by 2 hours. The use of ultrasound should precede scintigraphy for two important reasons: the size and the location of the lesion. Location of the lesion (anterior or posterior) is important for optimal gamma camera acquisition parameters. Lesions less than 1 cm are cannot be detected because they are beyond the limit of spatial resolution of the gamma camera we used.