Lymphoproliferative Disorder (LPD) is a complication of Methotrexate (MTX) therapy. Several cases of Methotrexate-Associated Lymphoproliferative Disorder (MTX-LPD) have been reported. However, pulmonary lesions in MTX-LPD are rare. Image findings of MTX-LPD show various patterns. Pneumocystis pneumonia and interstitial pneumonia, which have complex courses, have been reported in MTX-treated patients with lung diseases other than MTX-LPD. Furthermore, the treatment course of MTX-LPD differs from those of other lung diseases and could vary across patients. Here in, we discuss the importance of an accurate MTX-LPD diagnosis through detailed examination and treatment priority depending on the severity of underlying diseases and complications.