Nearly 5% of population suffer from excessive daytime sleepiness (EDS), thus making the condition a major social problem. However, decreased daytime wakefulness is mainly due to nocturnal sleep disorders (sleep apnoea syndrome, restless legs syndrome and/or insomnia), failure to adhere to a healthful regimen and sleep hygiene, drug and other types of addiction (alcohol, narcotics). The survey is directed to the newly introduced international classification of central hypersomnias including narcolepsy with and without cataplexy, a group of idiopathic and recurrent hypersomnias and secondary hypersomnias, possibly concomitant with organic and inorganic CNS involvement. The history of diagnostic and examination procedures, clinical picture and differential diagnostics has been briefly presented. Besides detailed history-taking and subjective scoring for EDS objectivization, a major role in diagnosing sleep problems is played chiefly by MSLT (multiple sleep latency test) and tests for some biochemical and immunological markers. The decreased levels of hypocretin/orexin in the cerebrospinal fluid and the presence of HLA-DQB1*0602 haplotype facilitate the diagnosis of narcolepsy-cataplexy. Modafinil is currently the best-tried drug for treating EDS and especially narcolepsy while sodium oxybate is a promising medicament for the management of cataplexy.

        Key words: excessive daytime sleepiness, diagnostic methods, diagnostic proof, differential diagnosis, narcolepsy, idiopathic hypersomnia, recurrent hypersomnia, secondary hypersomnia, central hypersomnia control