Background: Although in most patients the diagnosis of cystic fibrosis (CF) is made during their first years of life, a proportion of patients is diagnosed during adulthood. Aim: To describe the features of adult patients diagnosed with CF. Materials and Methods: Analysis of medical records of patients diagnosed with CF in a public hospital devoted to respiratory diseases. Demographic, clinical, laboratory and microbiological data were recorded. Results: Fifty eight patients aged 25.4 +/- 6.5 years were included. In 40% of them, CF was diagnosed after 15 years of age. The most common mutation found was Delta F508. Among clinical characteristics, lung involvement, mainly bronchiectasis, was found in 93%. The mean forced expiratory volume in the first second (FEV1) was 65,7 +/- 27,1%. Fifteen patients were colonized with Pseudomonas aeruginosa. The main complication seen was hemoptysis, in 12% of patients. Five patients died, mostly due to respiratory distress associated with sepsis, while three were subjected to bilateral lung transplantation. Patients in whom the diagnosis of CF was made after 15 years of age, had lower frequency of Delta F508 mutation, were most commonly women and had a lower rate of pancreatic involvement. Conclusions: CF is a disease that is increasingly reaching adult population. CF must be suspected in adolescents and young adults who suffer chronic lung diseases such as bronchiectasis, particularly when they are colonized by Pseudomonas aeruginosa, or in patients who develop infections by uncommon organisms. (Rev Med Chile 2012; 140: 841-846).