Structural metabolic changes in the biopsies of the large bronchi mucous membrane were studied in 99 patients with chronic lung diseases. Progressing sclerosis of the connective tissue stroma resulted in the reduction of endotheliocyte metabolism which usually represent plastically active zone of the strom. This considerably influences basal cell proliferation resulting in changes of differentiation in bronchial epithelium. Endobronchial laser therapy induces proliferative and metabolic processes in the tunica propria of the mucous membrane. Congestion, intensive leucodia pedesis, leucocytic infiltrates and granulations develop in the mucous membrane, proliferative and metabolic activity of endotheliocytes and stromal cells increases this resulting in formation of fine fibrillar connective tissue.