Philosophers concerned with what would be good for a person sometimes consider a person''s past desires. Indeed, some theorists have argued by appeal to past desires that it is in the best interests of certain dementia patients to die. I reject this conclusion. I consider three different ways one might appeal to a person''s past desires in arguing for conclusions about the good of such patients, finding flaws with each. Of the views I reject, the most interesting one is the view that prudential value is, at least partly, concerned with the shape of a life as a whole.