The alterations of the Cyclic Alternating Pattern (CAP) recently found in narcoleptic adult patients suggest the presence of an impaired modulation of the fluctuations of the arousal level during their non-rapid eye movement (NREM) sleep, possibly because of the persistence of neurophysiological mechanisms typical of rapid eye movement (REM) sleep. The same mechanism might play a role in the occurrence of leg movement (LM) activity during sleep characterized by low levels of periodicity. The aim of this study was to evaluate CAP and sleep LM activity in a group of children and adolescents with narcolepsy, to interpret the results under a developmental point of view and integrate this new information with data already available for adults. Thirteen young patients with narcolepsy/cataplexy were consecutively recruited for this study, together with 13 age- and sex-matched normal controls. Nocturnal polysomnography was carried out after a night of adaptation in a sleep laboratory room; sleep stages, CAP, and LMs were scored and evaluated following standard criteria. Narcoleptic patients showed shorter sleep onset and REM sleep latency, higher number of stage shifts and awakenings per hour of sleep, and higher percentage of wakefulness after sleep onset; CAP rate was found to be decreased in all NREM sleep stages (in particular CAP A1 subtypes) in narcoleptic patients who also showed significant higher values of all types of LMs (periodic or isolated), during both REM and NREM sleep; however, the most evident differences were found during REM sleep. The results of this study confirm that the sleep microstructure and LM activity changes observed in adulthood are already present and detectable in childhood and might have a role in the already known impaired prefrontal functioning of these subjects. The well-established orexin deficiency might be the unifying factor playing a major role in the modulation of CAP and LMs during sleep in children and adolescents with narcolepsy/cataplexy.