The antioxidant compound in green tea, EGCG, is in both caffeinated and decaffeinated green tea; however, decaffeinated tea may have lower concentrations of antioxidants due to the processing it undergoes. There are two main methods used: direct chemical solvent and supercritical carbon dioxide decaffeination. If you can, choose a decaf green tea brand that uses the carbon dioxide method as it preserves the most polyphenol content.