Dentofacial deformation is a common late adverse effect following radiotherapy for childhood head-and-neck tumours, yet current knowledge of dose-response relationships for developing facial bones and dental structures remains extremely limited. Age-adapted dose constraints and standardised clinical practices are lacking, complicating treatment optimisation and patient counselling. To address these critical gaps, we have established the SMILE consortium, a multi-disciplinary international collaboration of clinicians, scientists, and childhood cancer survivors. SMILE aims to establish structure-specific dose constraints, develop consensus guidelines including contouring atlases, and standardise follow-up protocols to minimise life-altering facial deformations and dental side-effects in future patients whilst better informing families.