Background: The purpose of this study was to calculate and compare the specificity and sensitivity of impulse oscillometry (IOS) as a new technique in the detection of airways dysfunction by means of a simple pulmonary function test in chemical warfare injured cases suffering from respiratory diseases. Methods: The study was performed prospectively in 100 patients, who complained of dyspnea as a result of sulfur mustard gas exposure in the Iran-Iraq war, between 1981 and 1988. Following a physical examination, IOS and spirometery were performed for all the patients. Then, the specificity and sensitivity of IOS parameters were calculated and compared with those of spirometery. Results: With a routine cut-off point, R at 5Hz and R at 20Hz have a sensitivity and specificity of 48.9%, 70.4% and 40.0% and 85.2%, respectively. With a normal cut-off point of R at5Hz=<240 or R at20Hz=<180 or x at5Hz=>-0.20 kpal/l/s, there is a 100% specificity (PPV=100%). Conclusion: While IOS is a new, cooperation independent technique and specific in the detection of airways dysfunction, it is less sensitive than spirometery in spotting small airways obstructions. IOS is a good diagnostic method in the detection of pulmonary involvements in uncooperative patients.