A very malnourished Cystic Fibrosis (CF) patient was treated with integrative Parenteral Nutrition (PN). With a mean caloric supplementation of 2,550 Kcal/day a weight gain of 6.5 Kg was achieved. In spite of severe pulmonary complications (pneumotorax and pneumomediastinum), pO2 increased from 53 to 72 mmHg and pCO2 from 38 to 56 mm Hg. General conditions improved, appetite was restored and the patient cleared off continuous oxygen therapy; he left the hospital and did not present any more pulmonary exacerbations. In the following 8-month period he maintained a daily caloric intake of 80 Kcal/kg with a further weight gain of 4.5 Kg.