Novel 6-bicyclopiperazinyl-1-arylsulfonylindole and 6-bicyclopiperidinyl-1-arylsulfonylindole compounds are disclosed which are useful as 5-HT6 receptor antagonists in the treatment of central nervous system disorders such as schizophrenia, depression, ADHD, and cognition and memory dysfunction The compounds are Formula I wherein: R1 is H or C1-4 alkyl; X is CH, —C—OR3, ═C, or —N and Y is C-R2 or N; R3 is H or —C(O)-R4; R4 is H or a labile prodrug group; n is 1 or 2; m and o are, independently, 0, 1, or 2 with the proviso that m+o is 1 or 2; and Ar is an aryl or heteroaryl group optionally substituted with 1-3 substitutents.