Flavones and flavonoids are known to have potent antioxidant activity due to intracellular free radical scavenging capacities. Flavonoids are found ubiquitously in plants as a member of polyphenolic compounds which share diverse chemical structure and properties. Quercetin is among the most efficient antioxidants of the flavonoids. The antioxidant property of quercetin has been highlighted in this review. These compounds have pivotal role in treatment of diabetes, cancers and some cardiovascular diseases.