Decaf coffee removes 97% or more of caffeine from green coffee beans before roasting. The method used , Swiss Water Process, CO2, ethyl acetate, or methylene chloride , determines how much flavor is preserved. Most bad decaf is the result of a poor decaffeination process on low-quality beans, not an inherent problem with decaf. This guide covers how each decaffeination method works, what it does to flavor, and how to find decaf coffee that actually tastes good.