The renin-angiotensin system (RAS) is an essential participant in the pathogenesis of several cardiovascular diseases. Currently, the most commonly used drugs affecting the RAS are angiotensin converting enzyme inhibitors (ACEi) and angiotensin receptor blockers (ARB). Their mechanisms of action are similar but not identical. The choice of specific compound is often based on clinical context. In the article, differences in therapeutic effects have been shown. Afterwards, a summary of results of clinical trials and therapeutic recommendations of leading international scientific societies, including arterial hypertension, chronic heart failure, coronary artery disease, and type 2 diabetes mellitus, have been presented. Finally, statements published by international scientific societies regarding abrupt changes in the treatment of cardiovascular diseases during the COVID-19 pandemic have been provided.