Advance healthcare decision-making presumes that a prior treatment preference expressed with sufficient mental capacity (“T1 preference”) should trump a contrary preference expressed after significant cognitive decline (“T2 preference”). This assumption is much debated in normative bioethics, but little is known about lay judgments in this domain. This study (N = 1445 US Americans; gender-balanced sample) investigated participants’ judgments about which preference should be followed, and whether these judgments differed depending on a first-person (deciding for one’s future self) versus third-person (deciding for a friend or stranger) perspective. We found that participants were more likely to defer to the incapacitated T2 preference of a third-party, while being more likely to insist on following their own T1 capacitated preference. Further, participants were more likely to conclude that others with substantial cognitive decline were still their “true selves,” which correlated with increased deference to their T2 preferences. These findings add to the growing evidence that lay intuitions concerning the ethical entitlement to have decisions respected is more a function of the relationship between the decision and the decision-maker’s true self, and less a function of the cognitive threshold of mental capacity, as in traditional bioethical accounts.