This study describes how demented immigrants' communicative performance together with caregivers who speak/do not speak these people's native language relates to the demented persons' cognitive, linguistic, and neuropsychological abilities. The study was carried out among demented persons who were born in Finland and had immigrated to Sweden. Their life history, linguistic history and linguistic behavior, and communication in standardized situations were assessed. Neuropsychological and medical examinations were performed for diagnostic reasons. The results show that many of these Finnish immigrants had difficulties communicating with their Swedish-speaking caregivers, while their communication with a Finnish-speaking caregiver was adequate. The frequent misunderstanding of a person's message often leads to a one-way communication, in which the caregiver commands and interrupts the demented person. The demented Finnish immigrants functioned on a level of manifest competence that seemed far below their level of latent competence. It seems reasonable that the presence of Finnish-speaking caregivers is an environmental change that would markedly enhance the demented Finnish immigrants' performance and quality of life and also reduce the costs for their care.