On the model of chronic obstructive pulmonary disease, the effect of therapy with low-molecular-weight peptides on restructuring and functional activity of bronchial epithelium for restoring the immune and barrier function of the lungs and prevention of inflammatory process progression was studied. Chronic obstructive pulmonary disease was modeled in rats by 60-day intermittent exposure to NO2. Administration of tetrapeptide Bronchogen for 1 month eliminates symptoms of remodeling of the bronchial epithelium and lung tissue typical of chronic obstructive pulmonary disease (goblet cell hyperplasia, squamous metaplasia, lymphocytic infiltration and emphysema, and restoration of ciliated cells). Enhanced production of secretory IgA, a local immunity marker, attested to normalization of functional activity of bronchial epithelium, while normalization of cell composition and profile of proinflammatory cytokines in the bronchoalveolar space reflected reduction of neutrophilic inflammation.