This diploma thesis deals with the constitutional development in Estonia in the interwar period, with particular reference to changes in the political system and the political reality. The Republic of Estonia gained its independence following the collapse of the Russian Empire in 1918, as a sovereign nation state under a democratic-parliamentary constitutional framework. Despite this rather favourable position, parliamentarianism was significantly weakened and a democratic-presidential constitutional framework was introduced, which subsequently developed into a presidential dictatorship. In addition to the comparative legal historical analysis of the constitutional texts, the constitutional reality and Estonia's political, economic and social developments are treated as well. This thesis consists of six chapters: after a short theoretical approach concerning the history and development of constitutional concepts in the first chapter, the second chapter deals with the development of the independent Republic of Estonia under two provisional constitutions. The third chapter contains the analysis of the Basic Law of 1920, which was the first final Estonian constitution. The fourth chapter deals with the constitutional amendment of 1933, which changed the Estonian constitutional framework in such a drastic way, that it can be seen as a wholly new constitution. The fifth chapter addresses the third Estonian constitution, the Basic Law of 1937. Following the substantive analysis of this constitution, it's subsequent application will be examined until the annexation of Estonia by the Soviet Union in 1940. This thesis concludes in the sixth chapter with a recapitulatory comparison of results combined with the final conclusions.