We report on a 17-year-old girl who developed steatohepatitis and marked weight gain during risperidone treatment for paranoid psychosis. Viral, metabolic, and other causes of liver disease were excluded. Although the exact mechanism of antipsychotic associated weight gain is unclear, the impact of risperidone on the serotonergic system and on neuropeptide Y, a stimulator of food intake, might be implicated in the development of obesity. Additionally, weight gain-related hyperleptinemia could be a link between overweight and hepatotoxicity via cytokines. Physicians should routinely monitor body weight, liver function, fasting blood glucose, and lipid profiles in children and adolescents at the beginning of risperidone therapy. Additionally, patients complaining about weight gain should be monitored more carefully during the maintenance phase.