Cystic fibrosis (CF) is a multisystem autosomal recessive disorder caused by the mutation of a single gene that encodes for the CF transmembrane regulator protein. Clinically, CF is characterized by chronic pulmonary infection, pancreatic insufficiency, and excessive losses of sweat electrolytes. Along with lung function, nutritional status appears one of the most important prognostic indicators in CF patients. In this study we examined the relationship between nutritional status and pulmonary function in adult CF patients. A group of 39 CF patients (mean age 23.9 +/-3.7 years) was studied. The mean value of body mass index (BMI) was 19.5 +/-2.9kg/m(2) (12.8-24.9kg/m(2)). The patients were grouped according to the presence or absence of malnutrition. Malnutrition was established in 11 patients (28.2%), 5 patients suffered from severe malnutrition. 28 patients (71.8%) had a normal nutritional status, but according to ESPEN guidelines, 9 of those patients were at risk of malnutrition. Statistical analysis revealed a significant difference between malnourished and not malnourished patients with respect to FEV(1)% and FVC%. Moreover, the patients with malnutrition were significantly more frequently colonized by P. aeruginosa and fungi and less so by MSSA.