Cancer in children and adolescents under the age of 18 is rare; in 2017, approximately 2220 new cases in Germany were reported to the German Childhood Cancer Registry. The aim of the GPOH has always been to treat as many affected patients as possible in a standardized way, preferably in prospective, controlled studies. The Joint Federal Committee has also laid down this requirement in the paediatric oncology guideline. In a survey among the study chairs of the GPOH, it was determined how the number of clinical trials has changed following the amended drug legislation. In 2002, 33 therapy optimization studies (TOS) of the GPOH were open. Overall, TOS decreased from 33 in 2002 to 2 in 2017. The number of drug trials has increased to 16 by 2017 (almost 1100 patients registered). At the time, the number of clinical registries has increased to 28 with a total of more than 1800 registered patents. This observation shows that the clinical registers have taken on a new significance in paediatric oncology. Three examples are used to examine what contributions registries can make in relation to studies on the treatment of patients and to scientific progress. In summary, the experience gained so far from the examples discussed illustrates that studies and registries mutually represent a meaningful and necessary addition to the study group structure in paediatric oncology.