Despite use of combined immunosuppressive agents, prognosis of patients developing pulmonary manifestations of chronic graft-vs-host disease (cGVHD) following allogeneic stem cell transplantation (SCT) still remains poor. We present a male patient who developed pulmonary cGVHD in the form of bronchiolitis obliterans organizing pneumonia (BOOP) following allogeneic SCT for acute myelogenous leukemia. The patient developed progressive course despite use of a combination of immunosuppressive agents including high-dose prednisone, cyclosporin-A, and mycophenolate mofetil in addition to steroid-related complications. A remarkable clinical response to extracorporeal photopheresis (ECP) was observed, allowing minimization of immunosuppressive therapy and discontinuation of cyclosporin-A. Pulmonary functions and carbon monoxide diffusion capacity (DLCO) gradually improved and stabilized, but did not return to pretransplant baseline levels.