Objective To study psychological adjustment in children and adolescents before undergoing heart or heart-lung transplantation and to reevaluate them at 6, 12, and 24 months after surgery. Methods Previously validated measures of behavior and depression were administered to children, their parents, and teachers. Parents also completed a measure of distress. Results Before transplantation, participants and parents obtained significantly higher scores on measures of behavior and psychological distress than children with no health problems and their parents, but 1 year after transplant, there were no significant differences between the two groups. Over time, there were significant improvements in depression and behavior scores in the group who had undergone transplantation. Conclusion Despite improvements in psychological functioning over time, a significant minority of children and adolescents undergoing transplantation are at risk for psychological adjustment difficulties. Psychological interventions to reduce morbidity need to be implemented and evaluated.