This study explored possible deficits in selective attention brought about by Dementia of Alzheimer Type (DAT). In three experiments, we tested patients with early DAT, healthy elderly, and young adults under low memory demands to assess perceptual filtering, conflict resolution, and set switching abilities. We found no evidence of impaired perceptual filtering nor evidence of impaired conflict resolution in early DAT. In contrast, early DAT patients did exhibit a global cost in set switching consistent with an inability to maintain the goals of the task (mental set). We discuss these findings in relation to the DAT literature on executive attention, dual-tasking, and working memory.