To clarify the relationship between morphological measurements of hepatic volume by computed tomography (CT-vol) and functional volume (RI-vol) by technetium-99m galactosyl human serum albumin (99mTc-GSA) scintigraphy, and its clinical significance, we examined 16 patients with a background liver status of either normal liver function (n=4), chronic hepatitis or cirrhosis (n=7), or obstructive jaundice (n=5). In five patients who underwent preoperative portal vein embolization (PVE), volumetric measurement was performed 2 weeks after PVE. The mean values of CT-vol and RI-vol of the right lobe were 692+/-147 cm3 (66.1+/-10.7%) and 668+/-159 cm3 (67.8+/-13.2%), respectively, and those of the left lobe were 329+/-138 cm3 (33.9+/-10.6%) and 328+/- 170 cm3 (32.2+/-13.2%), respectively. There were no significant differences in the volume measurements between the two volumetric techniques. Correlations between CT-vol and RI-vol in the right and left lobes were positive and significant (r=0.912 and 0.903, respectively; both P's<0.001). The mean values of post-PVE CT-vol and RI-vol of the right lobe in five patients were significantly different (628+/-149 and 456+/-211 cm3, respectively; P=0.033). However, the mean values of post-PVE CT-vol and RI-vol of the left lobe were not different (496+/-124 and 483+/-129 cm3, respectively). We propose that volumetric measurement by 99mTc-GSA scintigraphy is useful for detecting changes in functional volume of individual lobes of the liver and is a more dynamic method compared with detection of morphological changes by CT scan.