The REM sleep behavior disorder (RBD) is the parasomnia most commonly associated with an underlying neurological condition (the so-called symptomatic RBD). RBD usually occurs in setting of neurodegenerative diseases such as Lewy body dementia (LBD), Parkinson's disease (PD), and multiple system atrophy (MSA), and it may precede the development of Parkinsonism by many years. The disorders of arousal are the most frequent of the NREM sleep parasomnias. They may be triggered by prior sleep deprivation, alcohol, emotional stress and febrile illness. Different medications have been associated with RBD or REM sleep without atonia (RSWA), particularly psychotrophic and antihypertensive drugs. In the last two decades, some studies have demonstrated that arousals secondary to apneas, hypopneas and irregular breathing can be the trigger for sleepwalking and related disorders in children and adults. Hallucinations, both diurnal and nocturnal, have been described in PD associated with cognitive decline and RBD.