PURPOSE: The authors investigated the ability of cardiac blood pool clearance rates(CBCR) of 99mTc-DiSiDA in the measure merit of functioning hepatocyte mass. MATERIALS AND METHODS: We measured the volume of Iobectomized liver after completion of postoperative scanning with CBCR of 99rnTc-DISIDA in 5 rabbits who the functional hepatic Iobectomy performed by ligation of hepatic artery, portal vein and biliary tracts. Regarding the measurement of CBCR of 99mTc-DISIDA, we set the time which was decreased to the half of the clearance amount of the cardiac radioactivity by hepatic extraction of 99mTc-DISIDA at the point of 50 sec after the renal peak of the radioactivity to prevent confusing with the blood dilution of the radioactivity, that have called DI-K50. RESULTS: The results were followed that the volumes of the functional hepatic Iobectomy in 5 rabbits were 25%, 25%, 41%, 52%, 75% and the residual functioning hepatocyte masses measured by CBCR of 99rnTc-DISIDA were preserved to 75. 1%, 70. 8%, 63. 0%, 52. 2%, 30. 8% respectively. CONCLUSION: we made decision that CBCR of 99rnTc-DISlDA was useful to evaluate the functioning hepatocyte mass.