Brain tumors are the second leading cause of cancer in children. Primary tumors predominate and are of very varied histological types. Their prognosis and treatment depend on the histological type and grade. The diagnostic approach to these includes analysis of the site of the lesion and appearances on computed tomography and MR, and taking account of the age and clinical features of the child. CT is used to diagnose the tumor in an emergency situation. Conventional MR provides a morphological approach and allows a staging assessment to be carried out before surgery. Advanced MR techniques (diffusion-weighted and perfusion imaging, MR spectroscopy) provide further information for the differential diagnosis, presumptive diagnosis of type and grade and to guide biopsy towards the most malignant areas in the lesion.