The task undertaken by the Author of the article is to demonstrate that the countersignature is such a significant element of the system of government established in a given state that the existence or lack of the countersignature, as well as the method of incorporating it into the procedure of a given model of government, determines which particular system or which of its modifications had been accepted on the grounds of a given constitution.In the article it has been also proved that the constitutional principles have only general influence on the regulation of the countersignature. Many of them are necessary for the countersignature to function, however their establishment in the constitutional law do not determine the existence of the countersignature. The most important factors that decide whether this institution exist are compo- nents of the system of government, such as the dualism of the executive power and the assumption of lack of political responsibility of the head of the state. These features occur together within the parliamentary system. In order to prove the aforementioned thesis, a typology of the systems of government has been presented, then – after indicating the systems in which the countersignature does not exist and presenting the reasons of such situation – the countersignature and the form in which it has been adopted, in regard to the degree of the modification of the system, has been systematized.