CFTR modulators should improve the prognosis of Cystic Fibrosis. Identifying patients under the age of 18 responding to CFTR modulators as well as detecting possible toxicity is an important medical objective given the potential side effects and the high cost of these molecules. This observational follow-up cohort study is carried out as part of routine care. The main objective is to assess the evolution of pulmonary structural impairment by low-dose CF scan at the end of the first year of CFTR modulator therapy. The secondary objectives are to evaluate structural impairment at low dose scan at 3 years and 5 years of CFTR modulator treatment, the evolution of respiratory functional parameters, growth, puberty, lung infection, sweat test, quality of life and pancreatic function, as well as tolerance of modulators including liver toxicity.