Background: The aim of this study was to determine factors affecting sleep quality of 100 patients with advanced stage lung cancer. Methods and Results: it was a descriptive study. A variety of assessment tools were used to provide sleep scores to examine the relation between adverse effects caused by the treatment (nausea, vomiting, fatigue) and sleep quality. As a result, no statistically significant relation between coughing and respiratory problems of patients, or existing depression, and average sleep quality score was found (KW:0.872, p=0.646, KW: 3.174, p=0.205, u: 441.000 p=0.916). It was revealed that nausea and loss of appetite experienced also did not affect the sleep quality score (p>0.05), whereas problems such as vomiting and fatigue did exert effects (p<0.01). Conclusions: Patients with advanced stage lung cancer suffer from sleep problems and cancer related symptoms also affect their sleep quality negatively. Nurses should plan interventions that can control symptoms such as pain, vomiting and fatigue, which affect the sleep of patients.