Deep brain stimulation (DBS) is a clinically established procedure for treating severe motor symptoms in patients suffering from end-stage Parkinson’s disease, dystonia and essential tremor. Currently, it is tested for further indications including psychiatric disorders like major depression and a variety of other diseases. However, ethical issues of DBS demand continuing discussion. Analysing neuroethical and clinical literature, five major topics concerning the ethics of DBS in clinical practice were identified: thorough examination and weighing of risks and benefits; selecting patients fairly; protecting the health of children in paediatric DBS; special issues concerning patients’ autonomy; and the normative impact of quality of life measurements. In exploring DBS for further applications, additionally, issues of research ethics have to be considered. Of special importance in this context are questions such as what additional value is generated by the research, how to realise scientific validity, which patients should be included, and how to achieve an acceptable risk–benefit ratio. Patients’ benefit is central for ethical evaluation. This criterion can outweigh very serious side-effects, and can make DBS appropriate even in paediatrics. Because standard test procedures evade central aspects of patients’ benefits, measuring quality of life should be supplemented by open in-depth interviews to provide a more adequate picture of patients’ post-surgical situation. To examine its entire therapeutic potential, further research in DBS is needed. Studies should be based on solid scientific hypotheses and proceed cautiously to benefit severely suffering patients without putting them to undue risks.