Summary. The aim of this study was to investigate relationship between arterial stiffness and endothelial dysfunction, on one hand, and clinical ad functional parameters of chronic obstructive pulmonary disease (COPD), on the other hand. This was a prospective cross-sectional comparative study. Arterial stiffness was measured using photoplethysmography (Pulse Trace PCA 2, Micro Medical). We calculated stiffness index (SI) which reflected pulse wave velocity in large arteries, and reflectance index (RI) which is generally related to small vessel tone. Endothelial dysfunction was assessed with RI changes (Δ RISLB) before and after inhalation of salbutamol and also according to serum endothelin-1. The study involved 41 patients with COPD (mean age, 64.5 ± 7.6 yrs; FEV1, 37.7 ± 14.1 %; РаО2, 63.2 ± 11.2 mm Hg). SI was 11.3 ± 3.3 m / s; RI was 69.1 ± 16.6 % in comparison to 6.9 ± 0.9 m / s and 53.6 ± 14.7 %, respectively, in controls (р < 0.05). In COPD patients, Δ RISLB was significantly lower compared to controls (1.15 [0-10] % vs 11.50 [6–19] %; р < 0.05). As severity of COPD increased, Δ RISLB decreased (р < 0.05). Serum endothelin-1 in COPD patients was higher than normal level (0.47 [0.23–0.71] vs 0.26 fmol / ml; р < 0.05). Serum endothelin-1 was inversely related to RI (R = 0.44; р = 0.02) and Δ RISLB (R = –0.46; р = 0.03). A significant correlation was also found between the indexes and clinical and functional parameters (BMI, RV, DLCO, FEV1, heart beat rate, breathing rate, dyspnea assessment using MRC scale), 6-min walking distance. Therefore, arterial stiffness was significantly higher in COPD patients compared to patients with asthma and healthy volunteers. Increase in arterial stiffness is linearly related to severity of the disease. Endothelial dysfunction in COPD patients was significantly higher compared to that in comparative groups and was related to arterial stiffness.