Chronic obstructive pulmonary disease (COPD) and heart failure (HF) are both common diseases with major impact and seem to coexist more frequently than expected from their separate population prevalences. However, estimates of combined prevalence must be interpreted carefully because of imperfections and difficulties in assessment of both diseases. This review aims to highlight HF prevalence in patients with COPD and vice versa, with a critical analysis of studies performed. First, definition, diagnosis, and prevalence of COPD and of HF will be discussed. Subsequently, an overview of important studies concerning combined prevalence with their limitations will be presented. Finally, pathogenic mechanisms and diagnostic considerations in clinical practice will be discussed.