To assess the relationship between aspartate aminotransferase-platelet ratio index (APRI) and liver fibrosis in children with chronic hepatocellular and biliary cholestatic liver diseases. A retrospective review of one hundred children's demographic and laboratory findings concurrent with liver biopsy, who were followed-up with prolonged cholestasis. The diagnostic accuracy of the APRI was assessed by receiver operating characteristic (ROC) curves. Advanced fibrosis was more common in the hepatocellular group. The APRI values of the two groups were similar. The patients with advanced fibrosis had significantly higher APRI values than patients with mild fibrosis, in both the hepatocellular and biliary groups. The areas under the ROC were 0.68 and 0.81 in the hepatocellular and biliary groups respectively. The cut-off values of APRI for discriminating advanced fibrosis were 0.93 (65% sensitivity, 69% specificity) in the hepatocellular group and 2.35 (62% sensitivity, 96% specificity) in the biliary group. APRI may be most efficient for discriminating between advanced and mild fibrosis in biliary cholestatic liver disease patients.