Inclusion Criteria:  Patients with a cystic fibrosis diagnosis confirmed by a sweat chloride measurement ≥ 60 mmol/L Age between 10 and 20 years at enrolment Able to perform spirometry Having a smartphone Written consent adapted to the age Affiliated with a social insurance  Exclusion Criteria:  Antibiotic therapy for a pulmonary exacerbation in the 2 weeks before enrollment Lung transplantation (past or future) Colonization with Bulkholderia cepacia in the last 2 years Absence of contentment Inability to access technology required to transmit home spirometry data Inability to speak and read French well enough to understand the use of the home spirometry and to complete the questionaries