Purpose: Chronic obstructive pulmonary disease (COPD) is a health problem characterized by airflow limitation with resultant effects on respiratory system and other body systems. In this study, it was aimed to investigate the relationship between smoking history and functional capacity in patients with COPD. Materials and methods: Twenty-one patients with clinically stable COPD participated in this study. Patients' demographics, physical and physiological characteristics, duration from the diagnosis, and smoking history were recorded. Pulmonary function test and six-minute walk test (6MWT) were performed. Oxygen saturation using pulse oximeter and dyspnea and fatigue perception using modified Borg Scale were recorded before and after the 6MWT. Results: The mean age of the COPD patients was 59.4 +/- 8.8 years. The mean smoking history was 41.6 +/- 20.5 pack-years. Eight patients (38.1%) were current smokers. The mean forced expiratory volume in one second was 40.1 +/- 13.2% and the mean 6MWT distance was 477.0 +/- 104.4 m. Smoking history was significantly related with 6MWT distance (r=-0.47) and fatigue perception during exercise (r=0.52) (p<0.05). Conclusion: Prolonged smoking affects functional capacity and fatigue perception during exercise in patients with COPD. Smoking cessation should be a priority in the management of the patients with COPD.