The aim of this study was to analyze the impact of hypothalamic involvement of craniopharyngioma on functional capacity (FC) and obesity in 212 patients with childhood craniopharyngioma. FC could be evaluated using an ability scale (Fertigkeitenskala Münster-Heidelberg [FMH]) in 174 patients with childhood craniopharyngioma. Obesity was quantified in 212 patients at the time of diagnosis and at the time of latest evaluation by body mass index SDS [BMI]. The influence of hypothalamic tumor involvement on FC and BMI was analyzed. Patients with hypothalamic involvement (n = 125) presented with higher BMI SDS at the time of diagnosis (p = 0.001) and at latest follow-up evaluation (p < 0.001). FC as measured by FMH percentiles was lower (p < 0.001) in patients with hypothalamic involvement when compared with patients without hypothalamic involvement. FC negatively correlated (p < 0.001) with BMI SDS (Spearman's Rho = -0.40) only in patients with hypothalamic involvement whereas no correlation between FC and BMI SDS was found in patients without hypothalamic involvement. We conclude that hypothalamic involvement of childhood craniopharyngioma had major impact on FC in survivors. Obesity resulted in impaired FC of patients with hypothalamic involvement. BMI at diagnosis was a sensitive parameter to identify patients at risk of severe obesity. Further analysis on this issue is performed in the prospective, multicenter surveillance study on children and adolescents with craniopharyngioma (KRANIOPHARYNGEOM 2000).