Chronic obstructive pulmonary disease (COPD) is chronic inflammation leading to irreversible airway obstruction. Previous studies showed increased metalloproteinases (MMP) level, especially MMP-9, as a sign of local inflammation. Up-to-date, only a few studies estimated the MMP-9 serum concentration in COPD with respect to correlation with systemic inflammation. The aim of the present study was to estimate the MMP-9 serum concentration in COPD and to evaluate the correlation between MMP-9 and a degree of airway obstruction in COPD. Twenty three COPD patients and 23 healthy controls were enrolled. In both groups spirometry was performed. MMP-9 concentration in sera taken from both groups was studied using ELISA. We found that COPD patients had increased serum MMP-9 concentration compared with the control group (P=0.0005). In the COPD group, the MMP-9 levels were negatively correlated with FEV1 (P=0.01) and FEV1/FVC (P=0.0002). In conclusion, the results suggest that MMP-9 plays an important role in systemic inflammation in COPD. Higher MMP-9 serum concentration is connected with higher airway obstruction and disease progression.