Objective: The purpose of this study was to examine whether the degree of air trapping in high resolution computed tomography (HRCT) of patients with histories of sulfur mustard gas exposure during suspended full expiration correlated with various parameters of the cardiopulmonary exercise test as the gold standard for assessment of pulmonary function.Methods: In this analytic study 75 male patients, each with a history of sulfur mustard gas exposure, were investigated. Each participant underwent an incremental cardiopulmonary exercise test, pulmonary function test and arterial oxygen saturation for hemoglobin measurement. For HRCT examination, both lungs were divided into three parts (upper, middle, and lower) and in each part images were separately observed from the involved area point of view (<25% = <6/24; ³ 25% = ³ 6/24) .Results: A total of 49.3% of the patients (37/75) had evidence of air trapping in over 25% of their lung segments. The mean age±SD in the patients with air trapping of ³25% or < 25% were 41.1±6.8 and 39.7±4.0 years, respectively (P=0.281) . In our study there was no significant difference in pulmonary function test findings (FEV1, FVC and FEV1/FVC) between the two groups. There was no significant correlation with air trapping of ³25% and any of the exercise test parameters. Also, no correlation was found between significant air trapping and exercise test findings in maximum exercise and anaerobic situations.Conclusions: No correlation was found between HRCT and cardiopulmonary exercise test findings. HRCT is neither pathognomic of the disease nor a good predictor of disease severity but it might be suggestive of mustard lung injuries.