Objective To assess the role of diffusion tensor imaging (DTI) in detecting seizure foci which can not be seen in conventional MRI in patients with secondary generalized epilepsy.Methods The diffusion weighted imaging results were obtained in 30 adult patients with secondary generalized seizures and 30 healthy controls using Siemens 3.0T MRI system.The data from patients and controls were analyzed on basis of voxel-based analysis.Results Fractional anisotropy (FA) of the patients decreased significantly compared with the controls (P<0.001) in the right uniform gyrus and precuneus, right medial frontal gyrus and uncus, left cingulate gyrus, inferior temporal gyrus, cerebellar tonsils, and left precentral gyrus.Apparent diffusion coefficient (ADC) of the patients was significantly higher than the controls in the right parahippocampal gyrus, inferior temporal gyrus, corpus callosum, the right medial frontal gyrus, inferior frontal gyrus, cingulate gyrus, anterior cingulate gyrus, lingual gyrus, fusiform gyrus and occipital gyrus, left middle temporal gyrus, uncus and left precentral gyrus (P<0.001).However, ADC in the left gyrus rectus of the patients decreased significantly compared with the controls.Conclusions Extensive white matter microstructure abnormalities which cannot be seen on conventional MRI can be in patients with secondary generalized seizures by DTZ.