Nighttime eating is categorized as either night eating syndrome (NES) or the sleep-related eating disorder (SRED). Both diseases are often connected with an increase of the body mass, obesity, and with psychiatric disturbances. NES is characterized by evening hyperphagia, abnormally increased food intake after the evening meal, nocturnal awakings with ingestions, morning anorexia, and insomnia. Patients suffering from NES are aware of their nocturnal ingestions. It is suggested that NES is an abnormality in the circadian rhythm of meal timing that occurs in people with normal circadian rhythm of sleep. Other factors underlying NES include genetic predispositions, hormonal and neurochemical disturbances, and mood disorders. SRED is characterized by recurrent episodes of eating or drinking after arousal from nighttime sleep, unaware in tight the most cases, with adverse consequences. The distinctive features of SRED are amnesia of night eating episodes and consumption of non-typical food or dangerous articles. SRED is frequently associated with other sleep disorders, e.g., restless leg syndrome, periodic limb movement disorder, obstructive sleep apnea, and somnambulism. It can be also induced by medicines applied by a patient (e.g. zolpidem). It is hypothesized that the syndrome represents a variation of somnambulism. In the treatment of NES both non-pharmacological methods (psychotherapy, phototherapy) as well as the pharmacotherapy (aimed to increase serotoninergic neurotransmission in the brain, predominantly by sertraline, a selective serotonin re-uptake inhibitor) are used. SRED can be treated by controlling comorbid sleep disorders and eliminating provocative sedative hypnotics.