1,2-disubstituted heterocyclic compounds which are inhibitors of phosphodiesterase 10 are described. Also described are processes, pharmaceutical compositions, pharmaceutical preparations and pharmaceutical use of the compounds in the treatment of mammals, including human(s) for central nervous system (CNS) disorders and other disorders which may affect CNS function. Among the disorders which may be treated are neurological, neurodegenerative and psychiatric disorders including, but not to, those associated with cognitive deficits or schizophrenic symptoms.