Aim To evaluate apparent diffusion coefficient (ADC) characteristic of parenchymal neuro-Behcet's disease (NBD). Methods We retrospectively reviewed cranial magnetic resonance imaging (MRI) examinations of NBD patients with acute or chronic parenchymal lesions. ADC measurements of the lesions and contralateral normal brain parenchyma were performed by a consensus of two radiologists. To compare the ADC value of the chronic and acute lesions, relative ADC values (rADC) were calculated. The ratio of the lesions' ADC to contralateral normal brain parenchyma ADC yielded a rADC value of the lesions. Contrast enhancement patterns and the locations of the lesions were also noted. Results A total of 24 NBD patients with 45 parenchymal lesions, 25 acute, and 20 chronic, were enrolled in the study. A significant difference was observed between the mean ADC value of the acute lesions (1074.48 +/- 138.31 m/s) and the mean ADC value of the contralateral normal brain parenchyma (841.20 +/- 142.96 m/s; P < 0.0001). A significant difference was observed between the mean ADC value of the chronic lesions (1069.95 +/- 143.95 m/s) and the mean ADC value of the contralateral normal brain parenchyma (793.90 +/- 96.71 m/s; P < 0.0001). No significant difference was observed between the mean rADC (1.35 +/- 0.20) and the mean rADC value of the chronic lesions (1.29 +/- 0.15; P = 0.22). Conclusions ADC measurements might provide substantial information about the histopathological aspect of parenchymal NBD lesions.