This study aimed to analyse the relationship between supratentorial irradiation dose and the intellectual outcome in 36 children (aged between 5 and 15 years) treated for medulloblastoma. The supratentorial radiation dose was reduced to 25 Gy in 23 children and given at the standard dose, 35 Gy, in 13 other children. Neuropsychological evaluation was performed at a mean of 4.3 years (SD 4.7 years) after radiotherapy. The supratentorial radiation dose was the principal risk factor associated with impaired intellectual outcome. Verbal fluency, immediate word list recall, block design, and fine motricity of the dominant hand were significantly lower in children irradiated at the standard doses than in those irradiated at reduced doses. These findings suggest that the dose of radiotherapy applied to the brain strongly influences later verbal and non-verbal skills in children with medulloblastoma. This should be taken into account in treatment planning and in rehabilitation programs.