The invention describes for the first time the preclinical/cellular and clinical relevance of VIP, PACAP as well as of substances with the same biological activity as VIP and PACAP for the treatment of interstitial lung infections such as idiopathic pulmonary fibrosis, hypersensitive pneumonia or diffused panbronchiolitis. VIP and PACAP are synthesised in different areas of the central nervous system, e.g. in specific cerebral areas such as the hippocampus and the cortex, as well as in the peripheral ganglia. VIP is also released by immune cells.