Deep brain stimulation (DBS) is an established treatment option for some movement disorders, in particular Parkinson's disease. Only recently, a number of promising studies with small samples of patients have been published in which impressive therapeutic outcomes achieved by DBS in otherwise treatment-resistant obsessive-compulsive disorder, major depression, and Tourette's syndrome were reported. It seems probable that the investigational approach to treat mental disorders by DBS will increase substantially. Neurosurgical interventions in psychiatric patients raise ethical considerations not only based on the disreputable experiences of the era of psychosurgery. Therefore, it is necessary to implement transparent and well-defined regulations for the protection of the patients as well as appropriate support for therapeutic research. The current article aims to provide a synopsis of the DBS approach in mental disorders and the hitherto existing criteria for research. It suggests some additional requirements for ethically justifiable therapeutic research employing DBS in psychiatric patients.