The invention relates to the novel substituted 3-arylsulfonyl-pyrazolo[1,5-a]pyrimidines of the general formula 1, pharmaceutically acceptable salts and/or hydrates thereof, serotonin 5-HT 6 receptor antagonists and pharmaceutical compositions, and also to method for prophylaxis and treatment of various diseases of central nervous system at humans and warm-blooded animals pathogenesis of which is associated with serotonin 5-HT 6 receptors, in particular, Alzheimer's disease, Parkinson's disease, Huntington's disease, schizophrenia, and other neurodegenerative diseases, cognitive disorders and obesity. In the general formula 1: wherein: X = S, SO or NH； R 1 represents hydrogen, optionally substituted C 1 -C 3 alkyl, cycloalkyl, adamantyl, aryl or heterocyclyl； R 2 represents hydrogen, halogen, optionally substituted C 1 -C 3 alkyl, substituted hydroxyl, aryldiazenyl or optionally substituted amino group； R 3 represents hydrogen, optionally substituted C 1 -C 3 alkyl, substituted hydroxyl, pyridyl or optionally substituted amino group, besides, in cases when X = S or X = NH, at least one of R 1 , R 2 or R 3 represent substituted C 1 -C 3 alkyl, cycloalkyl, adamantyl, aryl, heterocyclyl, halogen, substituted hydroxyl, optionally substituted amino group, aryldiazenyl, or at least two of R 1 , R 2 or R 3 represent hydrogen； R 4 represents C 1 -C 3 alkyl； R 5 represents hydrogen, one or two halogens, C 1 -C 3 alkyl or optionally substituted hydroxyl.
