Using computed tomography (CT), measurements of whole liver volume have been used for the assessment of pre-operative functional reserve in cirrhotics. However, measurements of hepatocyte volume, which exclude stromal fibrous tissue, are considered to more directly reflect hepatic functional reserve. We investigated the relationship between total hepatocyte volume and each of the parameters of conventional liver function. Indocyanine green (ICG) tests and blood analyses for the assessment of liver function were performed prior to surgery in cirrhotic patients with liver tumours. Pre-operative liver volume was determined by integrating images of each liver area obtained by CT. Liver area was measured by an image processing program that traced the profile of the liver image while excluding the tumorous area. Sections of normal tissue stained by the haematoxylin-eosin method, were obtained from the resected liver. Using these sections, a hepatocyte area: whole tissue area ratio was calculated using the image processing program, by tracing the profiles of the hepatocyte nodules. The total volume of hepatocytes was then calculated by multiplying the liver volume by this ratio. The hepatocyte volume per unit bodyweight was significantly correlated with ICG tests and with many other parameters of normal liver function. However, the liver volume per unit bodyweight was correlated only with the plasma ICG disappearance rate and with the blood platelet count. These observations suggest that the functional reserve of the cirrhotic liver is assessed more precisely by hepatocyte volume than by liver volume.