Spirometry is a standard lung function test for diagnosis and staging of chronic obstructive pulmonary disease (COPD). Impulse oscillometry (IOS) can be complementary to spirometry, especially in patients at advanced age and with physical or mental disorders who cannot be diagnosed through spirometry. The aim of this study was to compare IOS and spirometry in the assessment of airway obstruction in COPD. The study was conducted in 112 stable COPD patients, including 29 females and 83 males of the mean age of 69±11 years. The oscillometric evaluation included total (R5), peripheral (R5-R20), and negative reactance (X5), which were compared with the predicted forced expiratory volume in 1 s (FEV1%pred). The findings show a significantly negative correlation between FEV1%pred and the R5, R5-R20, and X5. COPD patients had increased R5, R5-R20, and X5. The severity of bronchial obstruction found by impulse oscillometry correlated well the spirometric assessment. IOS is a simple to perform test that may be helpful for functional examination of COPD patients.