Preoccupation with the issue of public procurement comes up from the very fact that in this process procure and buy goods, services and works with budgetary and other public funds. This is not an insignificant amount of public funds, but a significant part of budget funds, which on a global level reaches up to 12% of GDP and 29% of budget funds. For this reason, public bodies are expected to effectively implement public procurement by applying the principle of 'best value for money' and with high standards of ethical and moral behavior. The targets of the research refer to the analysis of the applied public procurement instruments and the effects of reform changes in the public procurement system, the determination of relevant factors influencing the financial value of procurement and the determination of the relational relationships of influential factors on the effectiveness of public procurement. Through the application of the regression model, the research assessed the effect of relevant factors on the financial value of public procurement in the City of Zagreb as a representative basis for research and proof of the hypotheses. The selection of model variables is based on a theoretical analysis of the existing literature on unsolved issues and observed shortcomings in specifically set models, in order to test the set hypotheses. The variables included in the research model are: the financial value of procurement as a dependent variable and the estimated procurement value for a public procurement contract, the number of offers, the relevant legal framework - the Law on Public Procurement, determinants of green procurement, type of contract, selection method and type of procedure as independent variables. The results of the research confirmed that the instruments for the improvement of public procurement instruments contribute to the reduction of the financial value of procurement on five variables, and two variables (Law on Public Procurement and Green Procurement) did not show statistical significance of impact on the financial value of procurement. The application of the regression model confirmed the negative and statistically significant impact of the application of the “economically most favorable offer” criterion on the financial value of the procurement, thus proving that the application of the “economically most favorable offer” criterion enables the realization of the “best value for money” concept. However, further testing determined their significance in the research model. The regression model confirmed the negative and statistically significant influence of the “economically most favourable offer” on the financial value of the procurement, thus proving that the application of the “economically most favorable offer” criterion enables the realization of the “best value for money” concept.