This study assessed the utility of CT perfusion for quantitative assessment of liver function and fibrosis. Tissue blood flow (TBF), tissue blood volume (TBV), mean transit time (MTT) and hepatic arterial fraction (HAF) were measured with CT perfusion using the deconvolution algorithm in 38 patients with chronic liver diseases and 10 patients without liver disease. Using Child-Pugh classification, 21 patients were classified as Child A, 10 as Child B, and 7 as Child C. In 20 patients, the degree of fibrosis was quantitated in surgically-resected specimens and compared with the perfusion parameters. The mean TBF, TBV, MTT and HAF of patients with-out liver disease were 103.9+/-18 ml/min/100 g, 12.5+/-2.0 ml/100 g, 11.1+/-1.6 sec and 18.4+/-5.6%, respectively (+/-SD). The mean TBF of patients with Child A, B and C were 95.1+/-24, 86.7+/-29 and 75.5+/-6.5 ml/min/100 g, respectively. TBF tended to decrease with the severity of chronic liver disease. The mean HAF of patients with Child A, B and C were 18.6+/-8.3, 29.8+/-11.2 and 40.2+/-11.1%, respectively. HAF of patients without liver disease was significantly different from those of Child B and C (p<0.05, each). However, there were no significant differences in TBV and MTT between each groups. HAF correlated significantly with the degree of fibrosis (R2=0.588, p<0.05). Our results showed that parameters of CT perfusion correlated significantly with the severity of liver fibrosis and cirrhosis. Quantitative measurement of hepatic tissue blood flow by CT perfusion is useful for evaluation of the severity of disease and fibrotic change.