The purpose of this study was to detect the diagnostic value of diffusion-weighted magnetic resonance imaging in different pediatric cerebral diseases involving the cerebral white and gray matter and to compare the diffusion properties with age-matched normal children. Conventional and diffusion-weighted magnetic resonance imaging were performed in 21 children with various neurologic disorders and 25 normal control subjects. Apparent diffusion coefficients were measured from the brain lesions and 12 normal-appearing white and gray matter areas in the study group. Twelve normal-appearing areas were also measured in the control group. Apparent diffusion coefficient values obtained from the normal subjects were similar to values described in the literature but were significantly different from the control subjects. Apparent diffusion coefficient values for the neurodegenerative disease group (n = 8), the anoxic encephalopathy group (n = 4), the subacute sclerosing panencephalitis group (n = 4), the acute disseminated encephalomyelitis group (n = 3), and the encephalitis group (n = 2) were respectively between 0.29-1.85 x 10(-5) cm2/s, 0.13-1.87 x 10(-5) cm2/s, 0.96-1.57 x 10(-5) cm2/s, 0.49-0.73 x 10(-5) cm2/s, and 0.42-1.50 x 10(-5) cm2/s. Although this study is limited because of the size of the patient sample and disease heterogeneity, diffusion-weighted magnetic resonance imaging provides useful and complementary information regarding the degree of involvement in different pediatric neurologic disorders.