The tannins represent a highly heterogeneous group of water-soluble plant polyphenols that may play an important role in antimutagenic and antioxidant properties. We investigated the antioxidant function of tannic acid in comparison to other phenolic compounds including catechin, chlorogenic acid, cinnamic acid, ellagic acid, and gallic acid for their ability to scavenge several stable radicals and reactive oxygen species (ROS) such as ${ullet}DPPH^+$, ${ullet}ABTS^+$, hydrogen peroxide, hydroxyl radical, and superoxide radical. The ability of tannic acid to decrease paraquat-induced lipid oxidation in mouse liver and lung through its antioxidant properties was also assessed. The results showed that almost all the tested compounds have stable radical scavenging activity except cinnamic acid. Tannic acid, gallic acid, and ellagic acid demonstrated remarkable ROS scavenging properties toward $H_2O_2$, ${ullet}OH^-$, ${ullet}O_2^-$ and especially only tannic acid could inhibit paraquat-induced lipid peroxidation effectively in mouse liver and lung. Based on these results, it appears that increased number of galloyl and ortho-hydroxyl groups enhances the antioxidant activity of phenolic compounds and tannic acid is evaluated as the most effective antioxidant among all the tested compounds. These results suggest that the tannins, especially tannic acid, can be used as therapeutic agent for various diseases caused by ROS.