The objective of this study was to examine the integrity of whole-brain white matter in posttraumatic stress disorder patients. Twenty posttraumatic stress disorder patients who survived the Taegu subway fire incident and 20 healthy volunteers participated in this study. Statistical parametric mapping was used to evaluate the global differences in fractional anisotropy values between the two groups. The results show that posttraumatic stress disorder patients had significantly lower fractional anisotropy values in the left anterior cingulate regions. Posttraumatic stress disorder symptom severity negatively correlated to the level of decrease in anterior cingulate fractional anisotropy values. The outcome of the current study suggests that the disruption of the left anterior cingulate white matter tract integrity may play an important role in the pathophysiology of posttraumatic stress disorder.