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 a thought-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 "liberty principle"--correctly interpreted it does not support non-therapeutic research on cognitively impaired 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.