Background: Chronic obstructive pulmonary disease (COPD) is a progressive and debilitating disease. Cor pulmonale, characterized by right ventricular (RV) failure, can severely influence prognosis in these patients. Hence, early recognition might be important for tailoring therapy. An old biomarker, CA-125, seems to be associated with the right heart. We aimed to show the relationship between CA-125 levels and RV failure in patients with COPD.