Introduction: Regular physical activity (PA) is part of outpatient care offered to most people with cystic fibrosis (CF). Objective: To determine the frequency of the self-reported PA and, secondarily evaluate associations between PA with clinical variables and health-related quality of life (HRQoL) in pediatric and adolescent CF subjects. Method: In this cross-sectional study, subjects between 6 and 17 years of age with a confirmed diagnosis of CF were recruited in the outpatient clinic. The subjects answered questions about the practices of PA, HRQoL questionnaire and clinical variables were collected. Subjects were classified into two groups according to weekly PA practice: PA performed ≥ 3 times/week and performed PA ≤ 2 times/week. Results: 66 subjects completed the study, 72.7% (n=48) had PA ≥ 3 times/week and 27.2% (n=18) had PA ≤ 2 times/week. Only twelve children (18,2%) reached the recommendations of the World Health Organization (WHO) to practice moderate to vigorous physical activities daily. The mean age of the subjects evaluated was 12.3 ± 3.2 years, forced expiratory volume in one second 90 ± 24.1% and forced vital capacity 95 ± 20.4%. The group that performed PA ≥ 3 times/week had a better clinical score (p=0.033), a lower number of hospitalizations in the year (p=0.002), a lower number of days hospitalized in the last year (p=0.020) and better score for the physical (p=0.003) and emotion (p=0.048) domains in HRQoL questionnaire. Conclusion: This study concluded that most subjects did not reach the WHO recommendations for the practice of PA. However, individuals who practice PA at least 3 times/week have better HRQoL, clinical score and fewer hospitalizations.