The paper is devoted to the Czech banking system identification as a cybernetic system. The behaviour of banking system defined in this way is analysed here in the branch of capital cost management (bank loan). The aim of the paper is analysis of the managing system relations (regulator – central bank) to managed system (regulated cadre – commercial banks) as relationships between operational indicator (discount rate) and regulated indicator (commercial rates). The analysis encompasses the study of research time periods choice influence on research results. The main results of the paper are working conclusions related to structure and to behaviour of the Czech banking system as cybernetic system too and to impacts of structure and of such system behaviour on cost of capital management.