Bronchiolitis obliterans (BO) is a nonspecific inflammatory injury affecting primarily the small airways. Its inflammatory process is characterized by fibrotic obliteration of the lumen of bronchioles. BO can be idiopathic or associated with connective tissue disease, inhaled toxins, infections, drugs, and chronic graft-versus-host-disease (GVHD). Pulmonary complications occur in 40~60% of patients who undergo allogeneic bone marrow transplantation (BMT), causing 10~40% of transplant-related deaths. BO is a characteristic pulmonary complication which occurs usually within a few years after BMT. Documented complications of BO include air-leak syndromes such as pneumomediastinum, subcutaneous emphysema and pneumothorax. We report a case of a 30-year-old male patient with BO due to chronic GVHD after allogenic BMT who presented with recurrent bilateral pneumothoraces.