Pulmonary gene therapy offers the hope of treatment for conditions such as cystic fibrosis, lung cancer, pulmonary fibrosis and acute respiratory distress syndrome for which current therapy is inadequate. Although initial clinical trials in cystic fibrosis and non-small cell lung cancer have shown promise the results have not been as good as might have been anticipated. However, clinical improvement has been demonstrated in conditions such as haemophilia , cardiovascular disease , head and neck cancer  and X-linked severe combined immunodeficiency disease . The lack of success of pulmonary gene therapy is due, in part on the physical barriers to transfection perfected by the lung to prevent toxicity from inhaled particles, and partly due to the poor transfection efficiency of non-viral systems, and the immunogenicity of viral systems, of gene transfer. The LID vector goes some way to addressing the problems associated with current gene delivery strategies. With continued improvements in the properties of both viral and non-viral gene delivery systems leading to improved transfection efficiency with reduced toxicity, as well as the development of strategies aimed at reducing the physical barriers to pulmonary transfection, and targeting gene delivery systems to the site of injury, it is likely that pulmonary gene therapy will be used successfully to ameliorate a number of devastating pulmonary conditions.