The most common cause of death among patients with COPD is lung cancer as well as respiratory failure, and COPD often co-exists with lung cancer with a range of 40 to 70%.1 While lung cancer survival is generally very low, survival is even lower among patients with COPD, i.e. in one study, it is reported that 26% of lung cancer patients without COPD were still alive 3 years after their diagnosis compared to 15% of lung cancer patients with COPD.2 One of the reasons why prognoses of lung cancer patients with COPD are worse is that treatment options are limited due to affected lung function. For surgical treatment for lung cancer patients with COPD, post-operative residual lung function should be maintained within a certain level. Therefore, patients with severely reduced lung function may be rejected for surgical treatment, or at least they may not able to receive standard surgical procedures. For patients rejected for surgery because of poor lung function, radiotherapy is an alternative treatment option. However, radiotherapy itself affects lung function because of post treatment radiation pneumonia. For drug therapy, drug-induced lung toxicities are emerging issues, especially due to the use of EGF receptor tyrosine kinase inhibitors, ALK inhibitors or immune check point inhibitors.3 In cases whose lung function is severely affected, drug-induced lung toxicities may be lethal, and special attention should be payed to such patients. Therefore, to overcome these limitations of treatment is an urgent issue in the daily practice. For surgical treatment, assessment of preoperative lung function is essential to judge its indication. Both predicted post-operative lung function and DLco values are mainly used as parameters for the indication of surgical treatment. Therefore, optimization of these functions by medical therapy, pulmonary rehabilitation and smoking cessation may extend the opportunities of surgical treatment, resulting in better patients’ outcomes. Regarding with medical therapy, the Global Initiative for Chronic Obstructive Lung Disease (GOLD)4 and American Thoracic Society and the European Respiratory Society guidelines for COPD management point out the usefulness of bronchodilators as well as inhaled corticosteroids. In addition, pulmonary rehabilitations would be recommended for pre-operative lung cancer patients with poor lung function because of its safety, although there are no data clearly showing the efficacy of pulmonary rehabilitations on patients’ outcome. For radiotherapy for lung cancer patients with COPD, newly developed devices appear to show promising outcome. Both stereotactic body radiotherapy (SBRT) and ion beam radiotherapy have such a nice radiation dose distribution that high doses of irradiation are possible with low impact to normal tissues. Some reports suggest that patients’ outcomes by these treatment modalities may be not worse or sometimes better than surgical treatment.5 In addition, smoking cessation is, of course, important issue as a pre- and post- operative management. Since lung cancer patients with COPD are increasing over all area in the world, appropriate treatment should be chosen with the utmost care and attention. In addition, it is an urgent issue to establish more effective and safe treatment modalities to these patients. 1. Young RP, Hopkins RJ, Christmas T, et al. COPD prevalence is increased in lung cancer, independent of age, sex and smoking history. Eur Respir J. 2009;34(2):380-6. 2. Kiri VA, Soriano J, Visick G, Fabbri L. Recent trends in lung cancer and its association with COPD: an analysis using the UK GP Research Database. Prim Care Respir J. 2010;19(1):57-61. 3. De Sanctis A, Taillade L, Vignot S, et al. Pulmonary toxicity related to systemic treatment of nonsmall cell lung cancer. Cancer. 2011;117(14):3069-80. 4. Rabe KF, Hurd S, Anzueto A, Barnes PJ, et al. Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease: GOLD executive summary. Am J Respir Crit Care Med. 2007;176(6):532-55. 5. Chehade S and Palma DA. Stereotactic radiotherapy for early lung cancer: Evidence-based approach and future directions. Rep Pract Oncol Radiother. 2015;20(6):403-10. bronchodilator, stereotactic body radiotherapy, Surgery, lung function