In this dissertation a study of a decision support system (DSS) establishment in the rehabilitation planning of historic road bridges is given. The theoretical background of DSS, historic road bridges explanation, their characteristics and importance and potential rehabilitation methods are presented at a beginning of dissertation. Furthermore, the newly formed DSS has been designed and described as well as its basic elements: database, knowledge base, model base and dialogue. The research focus was in designing the model base, within which four new models are developed. The structure of the database has been presented and adequate data are collected as well as required knowledge to form a knowledge base. The collected data and knowledge influenced the modeling process in the model base. Through three levels of decision-making, an interaction between the mentioned basic elements of the DSS was established and its functionality was introduced. At the operational level, data were collected for databases such as: name and location of bridges, bridge characteristics, rehabilitation methods, spatial-functional and financial constraints and expert visual bridge condition estimation. At the tactical level, the way of forming goal three and relevant criteria for an individual bridge rehabilitation method selection are defined. A new model has been developed to assist in making tactical decisions in the selection of rehabilitation methods, based on defined criteria and a multicriterial approach using the AHP and PROMETHEE methods. After design of the model on tactical level, the model for rehabilitation priority ranking of all historical bridges on strategic level is developed. Thus, the methodology for criteria establishing, necessary for the realization of the newly developed model, is presented. These are the strategic criteria and as a result of the multicriteria methods (AHP, PROMETHEE and GAIA) application, the overall ranking of the analyzed bridges was obtained. Among the above mentioned criteria, is the criterion that presents historic road bridge condition evalutaion. Therefore, a new indicator called the Index of Historical Road Bridge Condition Rating (IHRBCR) was developed. The value of IHRBCR is the result of a newly established model of historic road bridges condition estimating. This model is based on combining a defined way of implementing expert visual bridge condition rating, modified fuzzy logic and multicriteria method (AHP). The overall rank of bridges, obtained as a result of the model for rehabilitation priority ranking of historic road bridges, with the definition of the necessary spatial-functional and financial constraints and their combination, was used for the realization of the newly developed model for manager's approach selection. As a result of the analyzed model, using the multicriteria method PROMETHEE V, a set of bridges for rehabilitation was obtained on an annual basis. The main goal of the dissertation is to develop a DSS that will assist the final decision-maker to carry out the rehabilitation planning of historic road bridges in the systematic and organized manner. The model was validated on the case of historic road bridges in the area of Split-Dalmatia County, built during or before the Austro-Hungarian Monarchy.