If a patient had just one advanced directive, the durable power of attorney would be the best choice for most. It is definitely the choice for anyone who can identify a friend or family member who can be trusted to make health care decisions consistent with his or her wishes. The durable power of attorney is far more flexible and comprehensive than the living will because the durable power of attorney simply designates an agent to make decisions when the client is unable. It does not forbid the withdrawal of nutrition and hydration and doesn't require that the patient be terminally ill before taking effect.

While the durable power of attorney is the more powerful document, there are advantages to using a DPA along with a living will if the living will is appropriately modified. Typically a DPA statute provides that a living will is not effective for anyone with a valid DPA. As long as the patient has a valid DPA the DPA controls.

But if a DPA should become unenforceable for some reason, a modified living will can fill the void for what might otherwise become a troublesome situation. The issue may arise and the following two circumstances: 1) The agent is unable or unwilling to serve. An agent may have died or become disabled. An agent, when it comes down to deciding whether to withdraw life support may be unable to make a decision. One way to address the problem is to name successor agents. However many people have a hard time identifying one, much less two agents. 2) The principle is outside Illinois, and the state doesn't recognize health care DPAs.

More states recognize living wills than DPAs, though most states recognize both, and the number of states that recognize DPAs is growing.

In either case, a properly modified living will conveys to physicians the patients desires about life sustaining treatment, something a DPA usually does not do. A DPA names an agent, but often does not give any specific information about the patient's wishes. The living will should contain a rider that contains their specific wishes which is likely to include removal of nutrition and hydration if they have a terminal condition. Terminal condition should be defined as broadly as possible.