Аннотация:Asthma and chronic obstructive pulmonary disease (COPD) are the main topics of modern pulmonology. Nowadays more and more scientists are concerned with search of methods of their prevention and treatment. More than 500 million people in the world suffer from asthma and COPD. Lately, the scientific community has been especially interested in studying these diseases in combination with concomitant pathology, including obesity. The goal was to measure the levels of leptin, asthmaiponectin, the degree of total oxidative damage (TOD), the total antioxidant status (TOS), IL-4, IL-6, TNF-α, neuropeptide Y, as well as the severity of clinical symptoms in patients with asthma and patients with COPD in various BMIs groups, and analyse the results when comparing with spirometry data. The research was carried out on 113 patients with asthma and 264 patients with COPD. There were 3 groups of patients within their nosology based on their BMI: with normal body weight (BMI: 18.5-24.99), overweight (BMI: 25-29.99) and obesity (BMI: 30 or more). Each patient had his individual registration card. The severity of symptoms of the diseases were assessed by using a certain set of scales and tests. All patients went through spirometry. Specific markers in blood serum were evaluated; in this research work have been analysed levels of leptin, adiponectin, the degree of total oxidative damage (TOD), the total antioxidant status (TOS), IL-4, IL-6, TNF-α, neuropeptide Y. All collected data were compared with the severity of clinical symptoms. Connections between the presence of obesity in patients with asthma and the following indicators in the blood serum were proved: the level of anorexigenic neuropetide Y, which causes insulin resistance - resistin, the level of TNF-α, the indicator of antioxidant activity of the body, and the degree of oxidative damage to biomolecules. As for patients with COPD, the following indicators were: levels of IL-6, TNF-α, leptin and resistin. Collected data allow us to summarize that obesity is a predictor of the disadvantageous course of asthma and COPD. To determine the influence of obesity on these diseases, the following serum indices can be used: leptin, resistin, TNF-α. Furthemore, for asthma neuropetid Y, the total oxidative damage and the total antioxidant status are prospective markers.