Kleine-Levin syndrome is a rare neuro-psychiatric disease. Most of the young patients are males who present with hypersomnia, cognitive dysfunction, altered perception, eating disorder (e.g. hyperphagia) or disinhibited behaviour (e.g. hypersexuality). Psychiatric symptoms such as apathy, delusions and hallucinations, depressed mood and compulsive behaviours also appear often and result frequently in a psychiatric referral. These symptoms, however, should be distinguished from those of psychiatric diseases as early as possible in order to ensure that patients do not receive the wrong treatment. We present the case of an 11-year-old boy in whom the psychiatric symptoms were initially the most prominent ones.