Regular exercise testing is recommended for people with cystic fibrosis (CF). In an international multicenter study conducted within the Exercise Working Group of the European Cystic Fibrosis Society (ECFS), we could recently demonstrate that cardiopulmonary exercise testing (CPET) derived variables provide important prognostic information on the combined outcome ‘death or lung transplantation (LTX)’ (Hebestreit et al. AJRCCM 2019). While this retrospective study focused on long-tern outcomes (up to 15 year follow-up), little information is available on the value of CPET outcomes on short-term survival and selection of lung transplant candidates. The planned project aims to assess the short-term (i.e., 2-year) prognostic value of CPET derived parameters in people with advanced lung disease that could potentially add important information to established parameters used for the selection of LTX candidates.