FLASH irradiations are very fast irradiations at very high beam currents, resulting in doses of tens of Grays delivered in hundreds of milliseconds. In these conditions, experiments in different animal models show that healthy tissues are spared for at least the same effect in tumours. The so-called ‘FLASH effect’ could substantially improve current clinical care, particularly for very aggressive tumours. One such case is Diffuse Intrinsic Pontine Glioma (DIPG), a paediatric brain tumour with a very low survival (2-year survival rate below 10%). DIPGs occur at a median age of 6-7 years and correspond to 10-20% of all childhood brain tumours. For these young patients radiotherapy is the standard of care, but outcome is limited by tumour location, invasiveness and aggressiveness. Early and long-term side effects occurring in these patients (memory alteration, intellectual decline, etc.) are limiting factors for the radiotherapy treatment.