Today no evidence based medicine analyses exist about the value of positron emission tomography (PET) in children and adolescents with Morbus Hodgkin. The increasing number of registered PET-examinations within the scope of the GPOH-HD 95 trial motivated to analyse the validity of 18-FDG-PET-examination findings in comparison to the conventional diagnostic methods (CT/MRI/ultrasound) and to the patients follow up. 67 PET-primary staging findings and 48 PET-follow up findings of altogether 106 patients from 27 PET-centres were analysed. Concerning the primary staging findings a concordance of 92% of the PET-findings and the findings of the CT/MRI/ultrasound-examinations per localisation was found, but in more than 50% of the patients a discrepancy occurred in at least one of the 9 investigated localisations. The analysis of the PET follow up findings showed a negative predictive value of 94% in regularly examinations (without previous suspicion of relapse), but only a positive predictive value of 25%. In case of relapse suspicion there was a negative predictive value of 83% and a positive predictive value of 76% in PET. A good prognosis is possible to predict from negative PET follow up findings (relapse risk in regularly controls 7%, at relapse suspicion 17%), whereas the probability for a true relapse in positive PET follow up findings is only markedly increased in case of former relapse suspicion (relapse risk in regularly controls 25%, at relapse suspicion 82%). A prospective multicenter PET study should be realized to analyse systematically the value of PET diagnostics in staging and restaging examinations of children and adolescents with Hodgkin's disease, especially to validate the PET diagnostics in exclusion of vital tumor residuals.