The aim of the study was to investigate 0.9% sodium chloride saline aerosol and airways electrical impedance including experiments with plastic tubes, healthy people and asthmatic patients examination using electrical impedance spirometry. The experimental part of the study consisted of measurements of the 0.9% NaCl aerosol particles size and their flow action on the electrical impedance measure in polyethylene tubes of different diameters. As a result reverse dependence between aerosol particles size, its flow intensity and electrical impedance value were revealed. In the clinical part of the study the mean values of the electrical impedance spirometry were detected in the children groups of different ages, healthy people and bronchial asthma patients. It was found that an active compound of electrical impedance spirometry was correlated with airways diameter and may be used as a criterion of bronchial obstruction syndrome. It was established that small airways disease is the basic mechanism of airways disorders in patients with control bronchial asthma, and small airways as well as large airways both are involved in not controlled bronchial asthma patients.