European Union Data Protection Directive, which came into force on 25th May 2019, casts new light on the aspect of data security in modern medicine and imposes a range of requirements on the administrators and subjects involved in personal data processing. This study discusses selected issues of personal medical data security with an emphasis on the area as sensitive as data security of psychiatric patients. The study underlines that the correctness and efficiency of personal data processing relies heavily on the cooperation of interdisciplinary teams i.e. medical staff, health informatics specialists, specialists responsible for the implementation of the policy of medical systems security and personal data processing, and lawyers.