Due to the ever-increasing role the LEADER approach is playing in realizing rural development policy, Local Action Groups (LAGs) have become key actors in the institutional system of rural development. Through their activity in supporting and improving local development, they represent a spatial organizing force in rural regions. Their operation can effectively contribute to the competitive and sustainable development of their local area, within the framework of European rural development policy. Compliance with this role requires the active and conscientious work of the LAGs, both in the process of programming and implementation. In this paper, we aim to present the impact mechanism of the operation of LAGs and its determinant factors. Based on expert evaluations, we investigate the experiences of the implementation of the LEADER approach for rural development from the viewpoints of effectiveness, efficiency and sustainability.