To evaluate the diagnostic utility of MR and CT in neurodegenerative diseases of childhood, we examined 63 children (MR in 44, CT in 53) carrying diagnoses of Leigh disease (14 patients), various metabolic diseases (13 patients), leukodystrophies (13 patients), other specific degenerative diseases (10 patients), and unclassified neurodegenerative disorders (13 children). Magnetic resonance yielded positive findings in 86% and CT in 81%. Lesion extent and conspicuity were consistently greater with MR. The high frequency of abnormalities detected on MR, and to a lesser extent on CT, helps distinguish children with neurodegenerative diseases from those with nonprogressive idiopathic movement disorders. The most common abnormalities included signal alterations (MR) or decreased attenuation (CT) of the basal ganglia and cerebral white matter, as well as local or generalized brain atrophy. Although considerable overlap was present, the findings showed four general patterns that may assist in tentative classification of patients with nonspecific clinical and laboratory findings.