The present invention relates to novel piperazine-piperidine compounds. The compounds are useful as 5-HT1A binding agents, particularly as 5-HT1A receptor antagonists and agonists. These compounds are useful in treating central nervous system disorders, such as cognition disorders, anxiety disorders, depression and sexual dysfunction. The invention relates to compounds and pharmaceutically acceptable salts of formula (I'): ##STR00001## wherein R.sub.1-R.sub.16, R.sub.a, R.sub.b, and n are set forth in the specification. The invention also relates to pharmaceutical compositions comprising compounds and pharmaceutically acceptable salts of formula (I').