Previous pathological investigations have reported bronchiolitis obliterans (BO) as the major long-term sequela of exposure to sulfur mustard. In this study, we investigated whether high-resolution computed tomography (HRCT) could be used as a noninvasive imaging modality to differentiate between mustard lung (as a subtype of BO) and other respiratory disorders. Three groups of patients with sulfur-mustard-induced lung injury (BO), severe chronic asthma (resistant asthma) and smoking habit, respectively, were recruited. Also 30 nonsmoking participants were recruited randomly as the control group. Pulmonary function tests (PFT) and HRCT were performed. Images were viewed with a window level of -450 and window width of 1,400 HU. All images were evaluated by an expert radiologist who was blinded regarding the patients' diagnoses and clinical situations. Airway involvement was higher and more frequent than parenchymal involvement in the groups with chemical-induced injury and asthma in comparison with smokers. On the other hand, parenchymal involvement was more frequent than airway involvement in the smokers' group in comparison with the other groups. HRCT can be a very useful method for differentiating between mustard lung, resistant asthma and lung injuries due to cigarette smoking.