The analysis of the maintenance of a metabolite of vitamin D (25-dihydroxyvitamin D) and vitamin D-binding protein in the blood serum of children under 3 years, patients with pneumonia. Found that a child with pneumonia is characterized by a significant decrease in blood serum concentrations of 25-dihydroxyvitamin D and vitamin D-binding protein. Additional risk factors for pneumonia in young children are adverse for the 2nd half of the pregnancy, the risk of miscarriage, the acute respiratory infections during pregnancy, a small body weight at birth; asphyxia at birth, a prematurity, the artificial ventilation in the neonatal period , artificial nutrition in the first year of life, the disease rickets, anemia, delayed motor development.