Advance directives or “living wills” are statements by competent adults setting out their wishes in anticipation of future incapacity to make decisions. The capacity to make independent choices and decisions may be impacted by mental illness，making advance directives of relevance to mental health law. Advance mental health directives allow competent individuals to specify their treatment preferences in advance of an incapacitating mental health crisis. Advocates believe that they can enhance autonomy and empower persons with mental illness to participate in their future treatment decisions. Opponents believe that they present a wide range of legal and ethical problems，making them unworkable in practice. The potential therapeutic，economic and human rights benefits demand their consideration in the Irish mental health context.