Aim. To evaluate the efficiency of nocturnal hyperalimentation in adult patients with cystic fibrosis (CF) and respiratory failure. Subjects and methods. The investigation enrolled 17 patients older than 18 years (mean age, 25.6±4.2 years) diagnosed with very severe CF (forced expiratory volume in one second (FEV1), < 30%; body mass index (BMI), < 18.5 kg/m2); all the patients were on the waiting list for lung transplantation. Nutritional status and pulmonary function parameters, such as body weight, height, BMI, and FEV1, were measured at baseline, before and 6 and 9 months after tube feeding. Results. The study group showed a considerable increase in body weight and BMI after 6 and 9 months. The change in lung function was statistically insignificant. Lung transplantation was successfully conducted in 5 patients; 4 died while on the waiting list; the cause of death was respiratory failure. Conclusion. Supplemental PEG tube feeding improves the nutritional status (BMI, body weight) of patients with very severe CF.