A novel piperidine derivative and a novel piperazine derivative which are useful as novel sigma receptor ligands, and an agent for treatment of diseases involving a central nervous system disorders, said agent containing one of the compound as an active ingredient. The agent contains a compound represented by general formula (I) or a pharmacologically acceptable salt thereof as an active ingredient: wherein X represents an alkylene group having 1 to 5 carbon atoms, and the alkylene group may be substituted by one or more alkyl groups each having 1 to 2 carbon atoms; Y represents a carbon atom or a nitrogen atom; and R1 and R2 each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 2 carbon atoms or an alkoxy group having 1 to 2 carbon atoms.