Three studies were conducted to measure health providers' beliefs about the personhood of long-term care residents with dementia, and the influence of these beliefs on health providers' intended actions toward patients in the long-term care contexts. In Study I, a Likert-format measure of health providers' beliefs about the personhood of long-term care residents with dementia (the Personhood in Dementia Questionnaire) was created after reviewing relevant literature and consulting with health providers. In Study II, this questionnaire was administered to a pilot sample of nurses and continuing care assistants. Psychometric analysis and subject matter expert review were used to reduce the length of the questionnaire to 20 items by deleting items that were less desirable from either theoretic or psychometric standpoints. The Revised questionnaire demonstrated good internal consistency reliability, and preliminary tests of external validity revealed a stronger correlation with a measure of beliefs about person-centered care than with a measure of beliefs about cancer treatment. Study III tested the criterion validity of the Personhood in Dementia Questionnaire by examining its significance as a predictor of health providers' responses to a health care vignette series. The Personhood in Dementia Quesionnaire, together with the cognitive status of the patients described in the vignette series was a significant predictor of all three intervention strategies identified as possible responses to the vignettes. Specifically, higher Personhood in Dementia Questionnaire scores were associated with an increased likelihood of considering pain medication and non-pharmacologic methods as intervention strategies. They were also associated with a decreased likelihood of considering anxiolytic medications. Overall, results from this study series show that it is possible to identify and measure health providers' beliefs about personhood in dementia. The results also provide initial evidence of the internal consistency reliability and of the external validity, including the criterion validity, of the Personhood in Dementia Questionnaire. The Personhood in dementia Quesionnaire can be used to evaluate components of person-centered dementia care interventions that target health providers' beliefs about the personhood of patients with dementia.