INTRODUCTION Sleep disturbance is common in dementia, impacting daytime function and care. Compared with Alzheimer's disease (AD), sleep in frontotemporal dementia (FTD) is poorly characterized. METHODS We assessed sleep using the Epworth Sleepiness Scale and Pittsburgh Sleep Quality Index in 58 people with primary progressive aphasia (PPA) and right temporal variant FTD, 32 with AD, and 36 cognitively healthy older volunteers. All participants had cognitive and behavioral assessments. Groups were compared using non-parametric statistics and correlations assessed sleep versus other indices. RESULTS Subjective sleep duration was increased in all syndromic groups. AD and semantic PPA were associated with increased daytime somnolence. Reported sleep quality varied between syndromes. Across the disease cohort, somnolence correlated with behavioral and empathy deficits; in AD, poorer sleep quality correlated additionally with self-monitoring deficits. DISCUSSION FTD and AD syndromes have distinct sleep phenotypes, and sleep alterations are associated with behavior. Standard sleep scales require careful interpretation in dementia.