Coenzyme Q10 (CoQ10) is an endogenously synthesized coenzyme and plays an essential role in ATP synthetic pathway. In Europe and America, CoQ10 has been consumed as supplement for more than 10 years, and recently it was approved in Asian countries. Since CoQ10 supplement is available without prescription, it is important to know its proper usage. CoQ10 exerts many beneficial effects for the treatment of disease. In hypertension, several clinical trials indicated that ingestion of 100-200 mg/day CoQ10 for 8-12 weeks significantly decrease systolic and diastolic blood pressure. Endothelial dysfunction is a functional prestep in athero-sclerosis, and administration of CoQ10 showed improvement of endothelial dysfunction in the patient with manifest endothelial dysfunction. CoQ10 has long been used as various heart disease, and its significant cardioprotection was demonstrated. In parkinson’s disease, CoQ10 treatment prevents disease progression, but higher dosage 300-1200 mg/day is required. Supplement dosage of CoQ10 for adult approximately ranges 30-100 mg/day. Overall, CoQ10 supplement seem to have beneficial effect on cardiovascular diseases, those including hypertension, heart failures and disturbed circulation.