To evaluate the efficacy of diffusion magnetic resonance imaging and compare with cerebrospinal fluid (CSF) flow imaging in patients with hydrocephalus before and after treatment. Twenty patients with hydrocephalus (group 1, pediatric, with primary aqueductal stenosis, n = 10; group 2, adult, with normal-pressure hydrocephalus, n = 10) and 20 age-matched healthy subjects that served as controls were examined. Cerebrospinal fluid flow velocity interval was calculated as the mean absolute values of the peak craniocaudal velocity and caudocranial velocity on CSF flow measurements. On diffusion magnetic resonance imaging, apparent diffusion coefficient (ADC) values from 8 regions were evaluated. The decrease in ADC values after treatment was significant in both groups (P < 0.001 for both). Preoperative mean CSF flow velocity interval value was significantly lower in group 1 and significantly higher than postoperative and control group values in group 2 (P < 0.001 for all). The ADC values increase in hydrocephalus and decrease significantly after treatment. Preoperative ADC value may serve as baseline, and the change in ADC may be an indicator of response to treatment and CSF flow measurements.