Objective. To determine the changes in liver function tests after long-term risperidone treatment in a child and adolescent population. Methods. Weight, alanine aminotransferase, aspartate aminotransferase, gamma glutamyl transpeptidase, alkaline phosphatase and serum bilirubin of the patients were assessed in pre-treatment period, and at the sixth and 12th months of treatment. One hundred children and adolescents (aged between 3 and 18 years) were enrolled to the study. Results. Liver enzyme and bilirubin levels are higher than normal in 21.0% of the patients without clinical symptoms. No cases of hepatic failure or jaundice were seen. Only in an 8-year-old boy were there ALT level increases up to three-fold and AST level increases up to two-fold. After discontinuation of the risperidone treatment, enzyme levels were normalized in this patient. Alkaline phosphatase, alanine and aspartate aminotransferases were the most frequently increased enzymes. Conclusion. In this study, after long-term risperidone treatment of children and adolescents there was no evidence of clinically significant increases of liver enzymes and bilirubin levels. These results indicate that risperidone treatment may rarely cause serious liver enzyme increases, and may commonly cause clinically insignificant changes in liver function tests.