Pulmonary complications of alpha interferon are rare. We report two cases of lung complications in liver transplantation patients for HCV related cirrhosis. After switching from interferon alpha to pegylated interferon alpha 2b, one patient developed a BOOP (Bronchiolitis Obliterans Organizing Pneumonia) and the other severe interstitial pneumonitis. We discuss the causes of these rare pulmonary alpha-interferon induced complications and the different way to suggest that the pegylated interferon alpha 2b could be related to the risk of pulmonary toxicity of this treatment.