Dementia with Lewy bodies (DLB) is the second most common form of dementia, and it is very frequently associated with changes in sleep patterns. To date, the literature has focused mainly on REM sleep behavior as the most prominent sleep disorder in DLB while little is known about the prevalence and the impact of sleep-disordered breathing (SDB) in DLB. Clinicians should be aware that the clinical diagnosis of SDB in DLB is difficult to establish and that the risk of overlooking SDB in patients with DLB is substantial. Polysomnographic sleep investigations may therefore be advisable in patients with DLB in order to objectify their sleep respiratory patterns. The available literature data on this topic, which are very limited and based on small case series, indicate that SDB occurs in 34.8 to 60% of patients with DLB. SDB can be hypothesized to coexist with other sleep-related disorders in an interactive loop: SDB alters sleep continuity, which can in turn facilitate nocturnal and daytime vigilance-dependent phenomena. There is an absolute need for prospective, preferably multi-center, controlled trials to establish whether, and to what extent, SDB might affect neuropsychological performances in patients with DLB and whether its treatment can improve residual daytime functioning in these patients.