Introduction/Objective. Alpha-1 antitrypsin deficiency is a well established inherited risk factor for chronic obstructive pulmonary disease (COPD); however, alpha-1 antitrypsin level may result in different lung function reduction. The aim of our study was to evaluate possible associations of alpha-1 antitrypsin level and lung function in COPD patients with different alpha-1 antitrypsin phenotypes. Methods. Serum alpha-1 antitrypsin concentration from patients (n = 1,167) with COPD, defined according to the GOLD criteria, were analyzed by nephelometry, and alpha-1 antitrypsin phenotype was determined by means of isoelectric-focusing. Results. In COPD patients without alpha-1 antitrypsin deficiency (MM), a significant negative association of lung function (FEV1) with serum alpha-1 antitrypsin (r = -0.511; p < 0.05) and C-reactive protein (CRP) concentrations (r = -0.583; p < 0.05) was detected; moreover, the level of alpha-1 antitrypsin positively correlated with CRP concentration (r = 0.667; p < 0.05). Conclusions. In patients without alpha-1 antitrypsin deficiency, detected negative association of alpha-1 antitrypsin level with FEV1 and positive association with the CRP level defined the importance of alpha-1 antitrypsin for lung function in COPD patients.