A living will (also referred to as a directive to physicians, health care declaration and medical directive) allows you to make decisions about your medical treatment should you become so ill that you are only being kept alive by life support systems. While a health care power of attorney allows you to decide who you want making medical decisions on your behalf, your agent would not be able to make the ultimate decision to shut off life support. However, most states now give you the power to specify through a living will under what circumstances you would want to discontinue treatment and shut off the machines keeping you alive artificially.  The living will may be incorporated into the health care power of attorney.