In the interwar period, intensified activity aimed at constitutional legislation is observed. This also concerned the Second Republic of Poland and the Republic of Finland, in which breakthrough acts were adopted. In Poland, two uniform constitutions were in force, significantly affecting the evolution of the state system in this period – the March Constitution of 1926 and the April Constitution of 1935. In Finland, one constitution was created, but of a complex nature – four legal acts were adopted in the period of 1919-1928. While in the Second Republic of Poland, in principle until the so-called May coup in 1926, the parliamentary tendencies were observed, in the Republic of Finland from the beginning, the executive power was equipped with strong competences, but within the parliamentary system. In Poland, as a result of adoption of the April Constitution, the state system was strongly turned towards authoritarianism. Both states saw their chance of maintaining independence in the pro-authoritarian tendencies, especially in the period preceding the II World War, due to the difficult geopolitical situation. In Poland, the authorities wanted to eliminate the chaos created by typical parliamentary governance. In Finland, this was not only related to the tradition of a strong executive, but more to the fear of potential revolutionary activities (like the Civil War of 1918) in the future that the head of state would be able to prevent.