Determine the activity of fecal β-defensin-2 and calprotectin and pro-inflammatory cytokines in young children with a mixed form of cystic fibrosis. The study involved 37 children with cystic fibrosis aged 2 months to 3 years, who were hospitalized in the Department of Gastroenterology RSSPMC of Pediatrics. It was found a four-fold increase in fecal calprotectin in children with cystic fibrosis compared with the control (p <0.001). Fecal β defensin-2 was increased 1.6 times in patients with cystic fibrosis (р<0.05). The results of measuring the activity of tumor necrosis factor alpha in children with cystic fibrosis showed an increase in its values in patients with cystic fibrosis - 6.9 + 2.3 ng / ml at a rate of 4.3 + 0.7 ng / ml (p <0.05). The highest results were observed in IL1 10.4 + 3.9 ng / ml (p <0.001), which reflects the increased activity of macrophages involved in maintaining the inflammatory process. Thus, there is clear evidence of intestinal inflammation in children with a mixed form of cystic fibrosis, which can negatively affect the patient’s nutritional status, which in turn adversely affects pulmonary function and survival. The data obtained are the basis for optimizing therapy aimed at improving bowel function.