Coronavirus disease 2019 (COVID-19) is found to be associated with various comorbidities which include cardiovascular diseases, hypertension, and diabetes. The impaired regulation of renin-angiotensin-aldosterone system (RAAS) has been seen in COVID-19 patients, but whether RAAS inhibitors, such as angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin II type 1 receptor blockers (ARBs), are responsible for worsening of clinical conditions remains unknown. Herein, we review the role of angiotensin-converting enzyme 2 (ACE2) expression in disease progression, its association with comorbidities and COVID-19, and summarize the clinical evidence for several potential directions for future research work on ACEIs/ARBs in COVID-19 patients.