The aim of the present study is determining the effect of Synbiotic supplementation on anthropocentric indices, quality of life, frequency of pulmonary exacerbation, frequency of hospitalization and antibiotic therapy in children with cystic fibrosis. This study is a clinical trial. The study population will consist of 40 children with cystic fibrosis. The inclusion are children with cystic fibrosis aged between 5-12 years. The exclusion criteria are having other disease including diabetes, cirrhosis, hypo-Albominemia, ventilator dependent respiratory failure. After measuring weight and height, BMI will be calculated and after then, the amount of antibiotic consumption, frequency of pulmonary exacerbation, frequency of hospitalization are recorded and gastrointestinal discomfort (diarrhea) and quality of life of children are evaluated and after getting the informed consent, the children will randomly assign to intervention or placebo group according to their age and sex. The patients in intervention group will receive 2 synbiotic capsules daily 2 hours after antibiotic treatment and the patients in placebo group will receive 2 placebo daily for 6 month. The primary outcomes are monthly measuring of weight, height, BMI, frequency of hospitalization and pulmonary exacerbation, bimonthly evaluation of oral or IV antibiotic receiving for 6 month, monthly assessment of diarrhea frequency and quality of life using pedsQL 4.0. For total antioxidant assessment, RANDOX kit will be used and for MDA assessment spectrophotometry method will be used.