Advance care planning is the process of preparing for possible future illness and incapacity by thinking in advance about what matters to you. These concerns can powerfully shape what medical treatments are right for you and, hence, what treatments you ultimately receive. Sometimes advance care planning relates to a future health state that is rare but devastating if it occurs, such as a serious accident causing head injury and coma, a persistent vegetative state, or profound cognitive dysfunction. Sometimes it addresses a future health state that is common with aging and in which many people would want medical care to be limited in some ways, such as dementia. And sometimes it focuses on a common complication or worsening of a chronic condition, such as heart failure, with which you have already been diagnosed and that you would want to be handled in a particular way.