There are few reports describing simultaneous occurrence of acute leukemia and lung cancer. We describe here an 83-year-old woman who simultaneously developed advanced adenocarcinoma of the lung and acute myeloid leukemia. She could not receive intensive chemotherapy due to poor performance status. This patient was treated with a combination of gefitinib, low-dose cytarabine and aclarubicin. This combination could be safely administered in the elderly patient with poor performance status and was effective for both lung cancer and acute myeloid leukemia.