Late-onset pulmonary complications after peripheral blood stem cell transplantation include various conditions such as opportunistic infections and interstitial pneumonias. It is sometimes difficult to diagnose interstitial pneumonias because there is substantial overlap in their computed tomography appearances. We present a case of an 11-year-old boy who consecutively developed pulmonary infection and cellular nonspecific interstitial pneumonia 9 months after peripheral blood stem cell transplantation for recurrent acute lymphocytic leukemia.