It is charaateristic feature of the serasonal adjusment procedures generally used today that their theoretical basis consists of analyses both in the time - and frequency - domain. However, both methods of analysis are unconnected hitherto. In addition, even the modern statistical concepts considering the transfer functions of the filters used, show definitorial deficiencies, since the lengths of the lengths of the relevant frequency bands are not determined objectively. Therefore in the following paper the problems of a possible connection of both methods of analysis and a solution of the aforementioned definitorial problems by using concepts of statistical estimation theory is analyzed.