Boron neutron capture therapy (BNCT) involves the use of a boronated pharmaceutical that accumulates in tumours to a greater extent than in surrounding normal tissues. When the tumour is exposed to a flux of epithermal neutrons, neutron capture by boron-10 produces high-linear-energy-transfer alpha particles and lithium-7 nuclei with short ranges, which can kill boron-containing tumour cells while limiting energy deposition farther from the capture site. While BNCT was first conceptualised 90 years ago, widespread clinical implementation was delayed because the original neutron sources were nuclear reactors and few clinically useful boronated drugs were available. Recently, accelerators producing adequate neutron flux of appropriate energy have become available, and more suitable pharmaceuticals have been developed, creating new opportunities for clinical implementation. BNCT has attractive characteristics for paediatric radiotherapy, and preliminary modelling suggests potential dosimetric advantages and a reduced risk of radiation-induced second cancers. The magnitude of any clinical benefit remains uncertain, as BNCT biological dose modelling is complex, normal tissue receives radiation from non-boron components of BNCT, and whole-body tissue exposure has not been evaluated. Here we review the potential benefits of BNCT in children, teenagers and young adults. Detailed clinical research programmes will be needed to evaluate the feasibility, value and toxicity of BNCT in paediatric practice.