The theoretical part of this paper deals with the history of banknotes in Croatia in 19th and 20th century. The features of the money and numismatics - as a scondary history science, have been explained. The causes of paper material degradation have been shown - as an introduction to the practical part of the study concerning preventive protection. In the practical part of this paper the inventory data are listed, the banknotes’ existing condition is described, the banknotes are divided into groups by degree of preservation, a proposal is made for the tests and analyzes, i.e. probe, pH analysis. Processes of mechanical cleaning, removal of adhesive tape, reinforcement of bend, pressing, and banknote storage are shown. The entire conservation process was followed by photodocumentation. I have chosen this particular paper subject due to the utmost importance of the banknotes denoting history and culture of Croatia and neighbouring regions. Conservation procedure was conducted in order to preserve the authenticity of the banknotes and prolong their life span. The value of the paper money, being one of the witnesses to the human social history is enormous, therefore this irreplaceable source of information must be preserved.