Protein-energy malnutrition with associated specific nutrient deficiencies is an important feature of cystic fibrosis and has been recognized as a poor prognostic factor. Therefore, the nutritional status of cystic fibrosis patients has to be evaluated regularly by diet diaries, clinical evaluation, anthropometry and more sophisticated methods, such as bioelectrical impedance analysis. Nutritional management, including nutritional rehabilitation programmes, of cystic fibrosis patients is well established today. Consequently, protein-energy malnutrition is no longer acceptable in cystic fibrosis patients, except perhaps in end-stage disease when lung transplantation is not considered.