Research on medical data is essential to the development of evidence based medicine. The use of medical data for scientific purposes must follow principles of good research practice and all relevant legal requirements. The aim of this article is to discuss ethical and legal aspects of processing, preparation and identification of medical data that were used by one of the authors for her doctoral research. The research deals with the black spots methods as a tool for minimizing risks of adverse events in medical setting. It must be stressed, that analyses presented in this article apply to research conducted by physicians as well as to research on medical data undertaken by representative of other medical professions, in particular physiotherapists.