Radiotherapy-induced late effects are severe, yet difficult to assess and quantify as they occur late and, therefore, often are the results of treatment regimens now considered outdated. Nonetheless, the risk of radiation-induced late effects is known to be influenced by both the radiation dose and the volume of irradiated tissue. In adults, the use of more conformal radiotherapy delivery techniques and breathing adaptation has been introduced in order to limit the irradiation of the surrounding healthy organs. However, there has been a reluctance to implement new radiotherapy delivery techniques in the treatment of pediatric patients as late effects data are not available for these new techniques and for the fear of a low compliance with breathing instructions.