Summary. Peculiarities of changes of lung function after bronchodilator were analyzed in this article. 67 patients with moderate stable COPD were investigated. All patients performed spirometry measuring slow and forced inspiratory and forced expiratory parameters and bronchodilatation test using 400 mg inhaled salbutamol. According to baseline FEV1 the patients were divided into two groups: 1 group – FEV1 30–50% predicted (mean 38.6±1.7%), n=30, 2 group – FEV1 51–80% predicted (mean 64.9±1.8%), n=37. It was determinate that FEV1 increased only 0.178±0.022 l for patients with more considerable baseline obstruction and there were no significant difference compare to baseline FEV1 (p>0.05). Meanwhile FVC significantly increased after bronchodilator (0.350±0.070 l, p<0.001) and was higher than DFEV1 (p<0.01). Analysis of the results of slow and forced inspiration tests showed that there were no significant differences between baseline IVC and FVC (p>0.05), however, IVC increased more than FVC after bronchodilator (p<0.05). It should be noted that for those patients baseline FIV1 was higher than FEV1 (p<0.001) and after bronchodilator FIV1 increased (0.318±0.040 l) more than FEV1 (0.178±0.022 l, p<0.001) too. In the 2nd group patients with less baseline airway limitation FEV1 increased significantly after bronchodilator but there were no differences between DFEV1 and DFVC (p>0.05). In spite of higher baseline FIV1 (0.022±0.061 l) than FEV1 (p<0.01) in this group there were no differences between both parameters after bronchodilator (p>0.05). Conclusion – in order to evaluate the reversibility of bronchial obstruction and treatment efficacy in COPD patients especially with more considerable obstruction it is recommended to measure not only FEV1 but also IVC and FIV1 changes after bronchodilator.