In 14 patients with hepatic tumors, liver volume and liver function indices were studied by 99mTc-GSA liver scintigraphy before and after hepatectomy. The liver volume measured by 99mTc-GSA SPECT was significantly decreased after surgery in all 14 patients (p < 0.001). Postsurgically, 7 patients showed an increase of greater than 10% in the LU15 value, while 3 showed a decrease of 10% in the LU15 value, while 3 showed a decrease of 10%. Two patients showed a decrease of greater than 10% in the HH15 value after surgery. The changes in LU15 after surgery were inversely correlated with those in HH15. The present findings clarified that in several cases of surgically treated hepatic tumors, 99mTc-GSA indices of liver function generally thought to indicate the size of the functioning liver cell mass were distinctly improved after surgery in comparison with those before surgery, despite the postoperative decrease in the liver volume. Furthermore, the results of a 99mTc-GSA SPECT study separately measuring the volume of the unilateral hepatic lobe and its radioactivity uptake, indicated that regeneration of the functioning liver cells often occurred in the entire liver. 99mTc-GSA scintigraphy appears to be a valuable method for evaluating changes in both the liver volume and the liver function indices after hepatectomy.