Diffusion tensor imaging (DTI) was used to measure the fractional anisotropy (FA) and apparent diffusion coefficient (ADC) value in amyotrophic lateral sclerosis (ALS) patients to determine their diagnostic value. 69 ALS patients and 23 healthy controls were scanned with DTI sequence in 3.0T MR, and FA and ADC values in 18 regions were evaluated. Compared with the controls, the ADC values of patients in bilateral centrum semiovale, deep frontal and parietal white matter were significantly increased (P < 0.05), while the FA values in cerebral peduncle, posterior limb of internal capsule (PLIC), corona radiata, centrumsemiovale, bilateral deep frontal white matter, the genu and the splenium of the corpus callosum were significantly decreased (P < 0.05). When the FA cut-off value was set to <= 0.6860 for the cerebral peduncle, sensitivity (SE) and specificity (SP) of ALS were 95.7% and 83.9% respectively. When the cut-off value was set to <= 0.7085 for PLIC, SE and SP were 95.7% and 85.7% respectively. When the cutoff value was set to <= 0.6950 for corona radiata, SE and SP were 100.0% and 95.7%, respectively. DTI can be used to quantitatively evaluate injury in ALS patients.