Evaluation of psychological well-being among persons with an advanced dementia is primarily dependent on verbal and non-verbal cues and behaviors that are observed and interpreted by others. The purpose of the present study was to determine how many components of psychological well-being can be measured. Fifty-seven individuals who were institutionalized for advanced dementia and exhibited agitation or withdrawal were evaluated by direct observations and by interviews with nursing home staff. Engagement was measured by the Lawton Positive Affect scale, visual analog scale, and reported degree of patient's interest in the environment. Mood was measured by a global indicator of mood interpreted from facial expression and two mood items from the Multidimensional Observation Scale for Elderly Subjects. Agitation was measured by a visual analog scale and by the Short Form of the Cohen-Mansfield Agitation Inventory. Correlation analyses and multidimensional scaling provided evidence for three dimensions of psychological well-being: engagement-apathy, happy sad mood, and calm-agitation. Evaluation of these three dimensions is important for measuring quality of care in long-term care settings and for determining effectiveness of therapeutic interventions.