Abstract. On the one hand, nutritive insufficiency is a typical symptom of cystic fibrosis, and on the other hand, can be considered as its complication. Chronic bronchopulmonary inflammation, increase of catabolism level, malabsorption of fat and protein, excess of viscous glycoproteids and increased amount of chalice cells in the small intestine lead to decrease of “availability” of nutritive substances. Nutritive disorders lead to weakness of respiratory muscles, reduction of lung volumes and development of hypoventilation, disorder of respiratory tract reparation, immune system dysfunction, aggravating severity of bronchopulmonary process. Modern strategy of nutritive support requires increase of calorie content of daily ration up to 120–200% per necessary weight, 40% calories being covered by means of fatty component, and 20% - by means of protein. We conducted observational clinical study of influence of application of special high-energy food product on physical development and life quality of children with cystic fibrosis. Materials for this study were indicators of physical development, data on history of development and disease of children (frequency of exacerbation periods of bronchopulmonary process during the study, need of urgent admissions to the hospital), and cultural study of respiratory microflora in 20 children aged 3 -6 years old. The level of physical development was evaluated by body mass index in the beginning and in the end of the nutritive therapy. We revealed that children who got supplementary nutrition as a component of daily ration during 6 months, had better indicators of physical development, which was expressed in larger values of body mass indices. Besides, among the patients who didn’t get regular nutritive support, we recorded increase in frequency of respiratory tract colonization with Pseudomonas aeruginosa.