Objective-To examine the contribution of neuropsychological test performance to treatment decision-making capacity in community volunteers with mild to moderate dementia.Methods-The authors recruited volunteers (44 men, 44 women) with mild to moderate dementia from the community. Subjects completed a battery of 11 neuropsychological tests that assessed auditory and visual attention, logical memory, language, and executive function. To measure decision making capacity, the authors administered the Capacity to Consent to Treatment Interview, the Hopemont Capacity Assessment Interview, and the MacCarthur Competence Assessment Tool-Treatment. Each of these instruments individually scores four decisional abilities serving capacity: understanding, appreciation, reasoning, and expression of choice. The authors used principal components analysis to generate component scores for each ability across instruments, and to extract principal components for neuropsychological performance.Results-Multiple linear regression analyses demonstrated that neuropsychological performance significantly predicted all four abilities. Specifically, it predicted 77.8% of the common variance for understanding, 39.4% for reasoning, 24.6% for appreciation, and 10.2% for expression of choice. Except for reasoning and appreciation, neuropsychological predictor (β) profiles were unique for each ability.Conclusions-Neuropsychological performance substantially and differentially predicted capacity for treatment decisions in individuals with mild to moderate dementia. Relationships between elemental cognitive function and decisional capacity may differ in individuals whose decisional capacity is impaired by other disorders, such as mental illness.Capacity for treatment decisions hinges on four legal standards, or abilities [1][2][3][4] : understanding (comprehension of diagnostic and treatment information), appreciation (personalization of information through integration with one's values, beliefs, and expectations), reasoning (evaluation of treatment alternatives in light of potential consequences for everyday life), and expression of choice (communication of a treatment Address correspondence and reprint requests to: Dr. Ronald J. Gurrera, VA Boston Healthcare System, 940 Belmont Street (116A), Brockton, MA 02301; Ronald.Gurrera@med.va.gov or Ronald_Gurrera@hms.harvard.edu. Disclosure: The authors report no conflicts of interest. It is logical to examine the neuropsychological correlates of decisional abilities for ways in which to refine their assessment, 8,19,24 and preliminary studies are encouraging with respect to the feasibility of this approach. 8,25,26 The authors evaluated the contribution of neuropsychological task performance to decisional abilities in community volunteers with mild to moderate dementia. They hypothesized that each ability would be significantly predicted by a distinct subset of neuropsychological tasks, and that understanding would be most, and expression of choice least, strongly associated with neuropsychologi...