In his paper, “The Relevance of Rawls’ Principle of Justice for Research on Cognitively Impaired Patients” (Theoretical Medicine and Bioethics 23 (2002):45–53), Giovanni Maio has developed athought-provoking argument for the permissibility of non-therapeutic research on cognitively impaired patients. Maio argues that his conclusion follows from the acceptance of John Rawls’s principles of justice, specifically, Rawls’s “liberty principle” Maio has misinterpreted Rawls’s “libertyprinciple” – correctly interpreted it does notsupport non-therapeutic research on cognitivelyimpaired patients. Three other ‘Rawlsian’ arguments are suggested by Maio’s discussion –two “self-respect” arguments and a “presumed consent” argument – but none of them are convincing. However, an alternative argument developed from Rawls’s discussion of “justice in health care” in his most recent book, Justice as Fairness: A Restatement, may justify certain kinds of non-therapeutic research on some cognitively impaired patients in special circumstances. We should not expect anything more permissive from a liberal theory of justice.