The impact of hepatic steatosis on regeneration of the remnant liver after living donor liver transplantation is unclear. We evaluated the impact of steatosis on regeneration and function of the remnant liver by using technetium-99m-diethylenetriaminepentaacetic acid-galactosyl human serum albumin scintigraphy. Twelve living donors were classified into groups with or without mild hepatic steatosis according to the liver-to-spleen attenuation ratio on computed tomography: 6 donors had a ratio >or= 1.20 (control group) and 6 donors had a ratio < 1.20 (fatty liver group). Scintigraphy was performed to determine the hepatic uptake ratio of the tracer (corrected for disappearance from the blood) and the maximum removal rate of the tracer by hepatocytes as parameters of the hepatic functional reserve. The fatty liver group had a significantly lower corrected hepatic uptake ratio and removal rate compared with the control group at 6 and 12 months after partial hepatectomy. These parameters were decreased at 1 month after surgery in both groups. However, both parameters returned more rapidly to prehepatectomy levels in the control group. The regenerated liver volume estimated by scintigraphy did not differ significantly between the two groups at any time. Liver scintigraphy may be useful for evaluating the regeneration of functioning hepatocytes. Because donors with mild hepatic steatosis showed impaired liver regeneration at 1 year after partial hepatectomy, management of these donors requires more care.