The classical narcolepsy patient reports intense feelings of sleepiness (with/out cataplexy), normal or disrupted nighttime sleep, and takes short and restorative naps. However, with long-term monitoring, we identified some narcoleptics resembling patients with idiopathic hypersomnia.To isolate and describe a new subtype of narcolepsy with long sleep time).University HospitalControlled, prospective cohortOut of 160 narcoleptics newly diagnosed within the past 3 years, 29 (18%) had a long sleep time (more than 11 h/24 h). We compared narcoleptics with (n = 23) and without (n = 29) long sleep time to 25 hypersomniacs with long sleep time and 20 healthy subjects.Patients and controls underwent face-to face interviews, questionnaires, human leukocyte antigen (HLA) genotype, an overnight polysomnography, multiple sleep latency tests, and 24-h ad libitum sleep monitoring.Narcoleptics with long sleep time had a similar disease course and similar frequencies of cataplexy, sleep paralysis, hallucinations, multiple sleep onset in REM periods, short mean sleep latencies, and HLA DQB1*0602 positivity as narcoleptics with normal sleep time did. However, they had longer sleep time during 24 h, and higher sleep efficiency, lower Epworth Sleepiness Scale scores, and reported their naps were more often unrefreshing. Only 3/23 had core narcolepsy (HLA and cataplexy positive).The subgroup of narcoleptics with a long sleep time comprises 18% of narcoleptics. Their symptoms combine the disabilities of both narcolepsy (severe sleepiness) and idiopathic hypersomnia (long sleep time and unrefreshing naps). Thus, they may constitute a group with multiple arousal system dysfunctions.