Cystic Fibrosis (CF) is a congenital disease secondary to the abnormal function of CFTR. Patients with CF have an alteration of essential fatty acids, Arachidonic Acid (AA) is increased and Docosahexanoic Acid (DHA) is decrease and the ratio ω-6/ ω-3 is elevated, all these alterations stimulated a chronic and bad regulated state of inflammation. For this porpoise, a fase IV trial, multicentric, controlled, double blind, placebo and parallel in patients elder than two months old and randomized to received every day a dietetically supplement with DHA or placebo, will be done during 12 months. The trial has as a principal objective to proved if this long term supplementation could decrease in contrast with placebo.

Inclusion Criteria:

• Diagnosed of cystic fibrosis over than 2 months age
• Tolerance clinical supplementation with DHA
• Clinical situation stable

Exclusion Criteria:

• Changes in the routine treatment in the 2 weeks prior to baseline
• Admission to hospital or administration of oral or intravenous antibiotics within 2 weeks before inclusion