To develop a method of modified set bronchophonography and set a diagnostic criteria of bronchial obstruction syndrome in young children. The study involved 60 patients with acute bronchiolitis and 60 healthy infants. We have developed the method of modified bronchophonography consisting of the registra-tion system of the respiratory noises and the personal computer. The analysis of respiratory noise was conduct-ed using the special software. Method of modified bronchophonography is important in the diagnosis of bron-chial obstruction syndrome in infants because of its objectivity, simplicity and accessibility of use in pediatric practice. New informative diagnostic criteria of bronchial obstruction syndrome in children has been estab-lished - E:I index, bronchial obstruction is diagnosed at E:I index≥1,20, bronchial obstruction is absent if E:I index≤1,19