Serotonin receptor 2C (HTR2C) is one of the attractive candidate genes for studying pathophysiology of mental disorders. Here we overviewed the genetic, expression and RNA editing studies suggesting the close relationship between HTR2C and major mental disorders including schizophrenia, bipolar disorder and major depression. We especially focused on the human studies as well as with reference to relevant cellular and animal models. Possible significance of genetic variations affecting expression and RNA editing and appropriate animal models that mimic human mental disorders were discussed.