The emotional well-being of persons with dementia is an aspect of their quality of life. We examined the stability of informant-rated and self-reported emotion, and the influence of mental status and physical dependence on ratings; we modeled concordance between ratings at both the within- and between-person levels of analysis. We used multilevel modeling to examine data collected over 12 days from 31 nursing home residents. We found significant within-person variation in both informant-rated and self-reported emotion, such that between 40% and 60% of the overall variance in each occurred within persons. We found little correspondence between or within persons between ratings of the informants and residents, regardless of mental status. We recommend statistical techniques that describe these high levels of daily variation in persons with dementia.