In this paper, I discuss whether it is ever morally permissible to diminish the cognitive abilities or capacities of some cognitively gifted offenders whose ability to commit their crimes successfully relies on them possessing these abilities or capacities. I suggest that, given such cognitive diminishments may prevent such offenders from re-offending and causing others considerable harm, this provides us with at least one good moral reason in favour of employing them. After setting out more clearly what cognitive diminishment may consist (...) of, I then critically discuss variations of four plausible arguments against a proposal of using them on cognitive gifted offenders related to autonomy, harm, narrative identity, and a right to mental self-determination. I argue that none of these concerns should have us reject the use of cognitive diminishments. (shrink)