Leptin and ghrelin are peptide hormones which, working antagonistically, regulate the energy balance of the body. The aim of the study was to evaluate the levels of leptin and ghrelin in the blood serum of patients diagnosed with cystic fibrosis (CF), in relation to their nutritional status and function of liver cells. The study group consisted of 34 patients, aged from 3 months to 18 years (mean age 4.5 years) who were diagnosed with CF on the basis of screening and/or diagnostic tests. The analysis included the nutritional status, CFTR gene mutation, assessment of the exocrine pancreas function, abnormal lipid metabolism, as well as liver cell function parameters. In all children, serum leptin and ghrelin levels were measured by means of an immunoenzymatic test, using reagents from DRG Instruments. The results were statistically analyzed. Serum ghrelin levels were significantly lower in the youngest patients (<1 year of age) compared with older age groups. A statistically significant positive correlation between ghrelin levels and amylase activity, and a negative correlation for serum lipase was observed. Ghrelin concentration was significantly lower in patients with salt wasting syndrome (p<0.05). The statistically lower serum leptin levels were observed in patients with growth deficiency and increased parameters of cholestasis, particularly in the youngest age group. Ghrelin and leptin levels in children with cystic fibrosis correlate with the nutritional status and can be an early marker of exocrine pancreatic insufficiency.