Aims: Chronic Obstructive Pulmonary Disease (COPD) represents a major health problem. Its prevalence is increasing worldwide. The aim of our study was to assess the relationship between markers of oxidative stress (malondialdehyde (MDA) and protein carbonyl) and the non-enzymatic antioxidants (vitamin E, vitamin C and reduced glutathione (GSH) with the marker of airflow obstruction (FEV 1% predicted) in COPD patients. Study Design: Case-control study.