The important role in legitimising the communist system of government in Croatia/Yugoslavia after the Second World War was played by the traditional institutions of legislative, executive and judicial government. Their organization in Federal State / People's Republic of Croatia began in 1943, and continued until the Constitution of the People's Republic of Croatia adoption on 18th January 1947, which gave them constitutional confirmation. As the supreme state governing institutions were declared People's Republic of Croatia's Parliament and its Presidium; Government of the People's Republic of Croatia was declared as the supreme executive and administrative governing institution, and Supreme Court of the People's Republic of Croatia was declared as the supreme judicial institution. In relation to their constitutional position, in previous researches of post-war political system in Croatia, was concluded that the real authority and decision-making monopoly had the highest body of the Communist Party of Yugoslavia, ie. Communist Party of Croatia. In doing so, the actual position and the role of republic governmental institutions in the communist system of government in Croatia after 1945 haven't been systematically researched, and this doctoral thesis makes a contribution in this scope. The doctoral thesis presents the results of researching the organisation and activity of People's Republic of Croatia's Parliament during the period of formal federalism and actual centralism (1945 – 1953). The aim is to explain the realation between the constitutional and actual position of the Parliament in the communist system of government, its structure, composition, legislative activity, relations with the Communist Party of Croatia/League of Communists of Croatia and republic governmental institutions, as well as the influence of its activities on everyday lives of the population. Parliament's organisation and activity is also compared to the organisation and activity of the National Assembly of Yugoslavia, as well as with legislative institutions of the former Yugoslavian republics and other European states with established communist rule, primarily Russian Soviet Federative Socialist Republic (RSFSR) and Union of Soviet Socialist Republics (USSR). A number of hypotheses are confirmed by research: the constitutional position of the supreme state governing institution, Parliament of the People's Republic of Croatia didn't achieve in practice; it was organized on the model of the National Assembly of Yugoslavia; its legislative activity didn't include the actual debate, but only a formal adoption and promulgation of pre-defined political goals and ideas of the Communist Party of Croatia/League of Communist of Croatia; in People's Republic of Croatia'a Parliament, there wasn't pluralism of political opinion; citizens addressed the Parliament, primarily with the aim of solving personal problems, especially social. Main methods used in research were critical analysis of resources (notably original, unpublished archival documents) and comparative method. The research results are presented by a combination of thematic and chronological approach. In certain chapters, they are systematized in the form of graphical and tabular overviews. Doctoral thesis is structured as follows. In the first, introductory chapter are explained the research topic, main goals, hypotheses and scientific contribution, methodology, as well as literature and resources used in the research. The chapter gives an overview of the previous researches relevant to the topic, and the classification of legislatures in such researches. The second chapter gives an overview of the Yugoslav/Croatian communist system of government and the position of legislatures in this system in theory. There are explained the main characteristics of the then revolutionary ideology of the ruling Communist Party, as well as formal constitutional provision. They are compared with the main characteristics of the Soviet communist system of government. It also gives an overview of the classical Marxist theory about the state, government and legislatures, and demonstrates how it was used in the writings and speeches of Yugoslav theoreticians and politicians. The third and fourth chapter give an overview of the People's Republic of Croatia's Parliament organization and activity in practice, divided into two chronological periods: until the adoption of the People's Republic of Croatia's Constitution in January 1947, and thereafter up in 1953. The fifth, concluding chapter, summarizes the main research results. Chapter six contains several appendixes: the results of parliamentary elections in Croatia 1946, 1947 and 1950; a list of councilors, ie. representatives in State Anti-fascist Council for the National Liberation of Croatia and in People's Republic of Croatia's Parliament 1943 – 1953; a list of members of the Presidium of the Parliament of the People's Republic of Croatia 1945 – 1953; a list of representatives from Croatia in Constituent Assembly of the Democratic Federal Yugoslavia / National Assembly of the Federal People's Republic of Yugoslavia 1945 – 1953; a list of laws adopted by the National Assembly of the Federal People's Republic of Yugoslavia 1946 – 1953; a list of tables and figures used in doctoral thesis). Seventh chapter contains a list of sources and literature used in the research. Doctoral thesis contributes to better understanding of institutions and the political system of government in Croatia in the period 1945 – 1953. Comparative approach in the presentation of research results, gives a contribution to knowledge of the political system of government and central governing institutions in the former Yugoslavia, as well in the other former Yugoslavian republics. At the same time, it can be a impulse for similar researces in those states. It also enables comparation with the political systems of government and legislatures in other European states with established communist rule. Through the analysis of the influence of its activities on everyday lives of the population, it gives contribution to the history of everyday life in communist Croatia and Yugoslavia.