Adolescents and young adults (AYAs) with hemato-oncological problems constitute a heterogenous group with characteristic particularities, specific needs, and age-related clinical and unique psychosocial features. Strong collaboration between pediatric and adult hemato-oncology settings is essential to address their needs appropriately. This is not only true for patients who first become ill during adolescence or young adulthood, but equally so for people who contract hemato-oncological diseases congenitally or as younger children and who are now becoming old enough to leave the pediatric setting and have to transit into "adult" medical care. Efforts to create environments that meet the specific needs of the AYA population affected by hemato-oncological diseases have been initiated in many countries. Due to international variations between societies in general and healthcare infrastructures in particular, the challenges posed to creating such environments vary considerably from country to country. Aiming at addressing these on a national basis for Germany, a dedicated Working Group on Adolescents, Young Adults, and Transition (Arbeitsgemeinschaft Adoleszenten, junge Erwachsene, Transition, AjET) was established. This meeting report depicts the content and discussions of the first interdisciplinary conference on treatment, transition, and long-term follow-up in AYAs with cancer or chronic/inborn hematological diseases. The AjET group of the German Society for Pediatric Oncology and Hematology (GPOH) intends to increase the national awareness for AYAs; strengthen the collaboration of pediatric and adult care givers; and initiate, promote, and coordinate collaborative activities in the fields of basic and translational research, clinical care, and long-term follow-up aimed at improving the current situation.