In this paper, I explore the role that regret does and should play in medical decision-making. Specifically, I consider whether the possibility of a patient experiencing post-treatment regret is a good reason for a clinician to counsel against that treatment or to withhold it. Currently, the belief that a patient may experience post-treatment regret is sometimes taken as a sufficiently strong reason to withhold it, even when the patient makes an explicit, informed request. Relatedly, medical researchers and practitioners often understand a patient’s post-treatment regret to be a significant problem, one that reveals a mistake or flaw in the decision-making process. Contrary to these views, I argue that the possibility of post-treatment regret is not necessarily a good reason for withholding the treatment. This claim is justified by appealing to respect for patient autonomy. Furthermore, there are occasions when the very reference to post-treatment regret during medical decision-making is inappropriate. This, I suggest, is the case when the decision concerns a Bpersonally transformative treatment^. This is a treatment that alters a person’s identity. Because the treatment is transformative, neither clinicians nor the patient him/herself can ascertain whether post-treatment regret will occur. Consequently, I suggest, what matters in determining whether to offer a personally transformative treatment is whether the patient has sufficiently good reasons for wanting the treatment at the time the decision is made. What does not matter is how the patient may subsequently be changed by undergoing the treatment.