Despite several efforts to improve the transparency of the EU decision-making and address various sources of the Union’s democratic deficit, there is still a widespread perception of the community as a "political space without political life”. Given the internal and external crises the EU has been facing in recent years, including the epidemiological and migrant crises, unclear enlargement policies, the loss of a member state, the deterioration of rule of law situation, as well as growing populism and Euroscepticism in some member states, the need to invest in building public trust in the EU institutions has been increasingly emphasized. There is still a lack of knowledge about the participation and influence of interest groups in the open EC public consultations on draft legislative acts, and specifically, the lack of research on the involvement of interest groups from Croatia (the newest member state) in these consultations. Therefore, the main research question in this thesis is to what extent interest groups use the European Commission's open public consultations to influence EU decision-making. More specifically, the case of Croatia will be used to explore this field through analysis of available data from the EU Transparency Register and Have Your Say portal. The expected contribution of this thesis in providing new knowledge on domestic interest groups involved in policymaking, while simultaneously examining how much public consultation is affirmed at the national level, and what motivates interest groups to participate in the most important- supranational decision-making processes.