Introduction: Butyrylcholinesterase (BChE) is involved in the metabolism of endogenous lipids and xenobiotics, such as esters of carboxylic or phosphoric acids. Butyrylcholinesterase activity is associated with both inflammation and oxidative stress. Changes in the activity of this enzyme have been observed in various diseases such as liver cirrhosis, diabetes, neurodegenerative disease and others. Material and methods: The study involved 30 patients with chronic obstructive pulmonary disease (COPD) and 18 healthy subjects. The COPD patients were divided according to the severity of the disease by applying the classification of COPD based on GOLD standards for forced expiratory volume in 1 s (FEV1) and the FEV1/forced expiratory volume (FVC) ratio. The control group comprised blood samples collected from healthy subjects without concomitant diseases related to the respiratory system. Butyrylcholinesterase activity, lipid peroxidation and total antioxidant capacity (TAC) were determined in the blood plasma. Results: A significant (p < 0.05) decrease in the activity of BChE, associated with an increase in lipid peroxidation and a decrease in the total antioxidant capacity, was observed in blood plasma of patients with chronic obstructive pulmonary disease. Conclusions: The study shows for the first time that activity of BChE in the blood plasma of patients diagnosed with chronic obstructive pulmonary disease is considerably reduced compared with healthy subjects. These changes were accompanied by a decrease of TAC and an increase of lipid peroxidation, which suggests that they may be related to the oxidative stress induced by COPD disease.