The goal of this diploma thesis, which is related to the nature, interconnections and differences of external and internal audit, is to bring interested persons closer to the reason for inception of external and internal audit and to define their position and importance in 21st century. Approximation of both audit's contents and going, with regard to their goals, is naturally also a part of work. A piece of work is particularly devoted to external and internal auditor's personality and thus to personal and professional demands for such profession. Not forgotten is the legal adaptation of both audits and it is explain, which audit is under more strict adaptation and why. In the thesis conclusion is located an external-internal auditor compar...