Purpose: Recently, several studies suggested the relationship between sleep disordered breathing (SDB) and cancer progression. It has been well established that hypoxia plays an important role in regulating the various stages of cancer formation and progression. The aim of this study was to investigate the prevalence and effects of SDB in patients with lung cancer. Methods: A total of 19 patients who were histologically confirmed with lung cancer were enrolled in this study. Daytime sleepiness was assessed using the Epworth Sleepiness Scale (ESS) and Sleep quality was assessed using the Korean version of the Pittsburgh Sleep Quality Index (PSQI-K). SDB was defined as an apnea- hypopnea index (AHI) of > 5/h, using a two-channel screening system (ApneaLink™). Results: The overall prevalence of SDB was 54.5% in total patients with lung cancer and 62.5% in patients with adenocarcinoma. The median AHI was 5.9 [3.1; 11.8] and the median oxygen desaturation index was 8.3 [4.0; 14.1]. The mean value of the lowest oxygen saturation was 82.8±7.0% and the median time of oxygen saturation under 90% was 10.0 minutes [5.5; 33.0]. The median ESS score was 6.0 [4.5; 10.5] and mean PSQI-K was 5.9±4.3. There was no significant difference in clinical indexes according to the presence of SDB, except the sleep parameters. Conclusions: These results showed a high prevalence of SDB in patients with lung cancer. Further research is needed to find the relationship between SDB and pathogenesis of lung cancer.