OBJECTIVE: Validating a German child-friendly version of the EuroQol (EQ-5D) in different patient samples. METHODS: After the translation from the original English version and pre-testing in cognitive interviews with native speakers of the target language, the questionnaire was tested in two patient groups (obesity and CF) and a sample of healthy children between the ages of 8 and 16. For the validation three validated instruments which measure hrQol in children and adolescents were utilized (KINDL, KIDSCREEN and ChildDynHA). T-Tests were conducted to audit potential differences in the EQ-5D scores depending on age and sex of the children. Descriptive statistics were used to summarize EQ-5D scores as wella s scores of the additional instruments RESULTS: The correlation between the EQ-5D and the other instruments was quite high (0.46 - 0.61). The highest correlation was found in the mobility dimension. The CF groups shows the highest rates of reported problems (42%), the rates of children who report no poblems are quite similar for the obese and the healthy children (25 versus 27). CONCLUSIONS: This pilot study of the questionaire showed that the German child-friendly version of the EQ-5D is a valid and feasible instrument to measure hrQol.