━━ Background. We herein report a case of granulocyte colony-stimulating factor (G-CSF) -producing lung cancer in an elderly patient who showed improvement in her performance status after surgery. Case. An 89year-old woman had difficulty walking outside due to fatigue and dyspnea on exertion, and her activities of daily living had declined to a performance status of 2. A 7.9×5.0-cm mass lesion was found in the lower lobe of the right lung, and blood tests showed a high white blood cell count of 17810/μl and serum G-CSF level of 211 pg/ml, leading to suspicion of G-CSF-producing lung cancer. The operation was performed under thoracotomy. It was determined that the tumor had spread to the intermediate bronchus and that preservation of the middle lobe was not possible, so the middle and lower lobes were resected. G-CSF staining of the resected specimen showed positive findings in the cytoplasm of some tumor cells. Although the patient was elderly, complete resection resulted in resolution of her fever and improvement in her postoperative activities of daily living to a performance status of 1. Conclusion. G-CSF-producing lung cancer has a poor prognosis, and no standard treatment has yet been established; however, surgical resection should be attempted whenever possible, as it may improve symptoms associated with the tumor and prolong the survival.