Plasmacytoma are extramedullary accumulations of plasma cells. Most extramedullary plasmacytomas are associated with the upper respiratory tract. The lung is rarely involved. We report a rare case of lung plasmacytoma with multiple myeloma. The patient is a 60-year-old male who presented with chest pain and a lung mass visualized on CT scan. A preliminary diagnosis of occult lung cancer with widespread skeletal metastasis was made. The diagnosis of lung plasmacytoma with multiple myeloma was made after extensive investigations.