Paraneoplastic neurological syndrome (PNS) is a rare disorder caused by the remote effects of cancer and is considered as immune-responses to the molecules on cancer which cross-react with self-antigens in the nervous system. Since the 1980s, several specific anti onconeural antibodies have been reported, which are useful diagnostic markers of PNS and occult cancer. Only a few onconeural antibodies have been identified as primary effectors of neurological damage. Recently sophisticated methods for the detection of new or low titer antibodies have been developed. Several new auto-antibodies against receptors or ion channels on the surface of neuronal membrane, such as NMDA receptors, AMPA receptors, GABA(B) receptors and VGKC complexes, have been reported in the patients with encephalopathy including limbic encephalitis. These diseases can be associated with tumor, but they are more often non-paraneoplastic. These antibodies are generally good biomarkers for effective immunomodulatory treatment for immune-mediated encephalitis with not only consciousness disturbance but also dementia, seizures and psychiatric symptoms which sometimes mimic schizophrenia. Further studies are required to clarify the exact mechanisms underlying neuronal damage in immune-mediated neurological diseases including PNS, which may lead to the development of more rational therapies and greater understanding of immunology in the nervous system.