The principle of separation of powers is among those rules governing proper functioning of the State which accompany the reflection about the exercise of State authority since it has become the subject of discussion concerning the attributes of a government the people deserve. This question attracts interest of constitutionalism since its birth. At the same time, the separation of powers principle has become the subject of many critical assessments and comments focused on the practice of functioning of constitutional systems based on that principle. However, their functioning is not free of mistakes and failures; and the principle itself helps the governments justify their lack of effectiveness and discourages the ordinary citizens from participation in public life. It is also perceived as an anachronism , as compared to the opportunities of new technologies and challenges of development. It might be said, however, that this principle, typical of democratic state governed by the rule of law, constitutes - especially in the context of threats to modern democracy - a determinant of identity of constitutionalism, on account of its importance for the affirmation and guarantees of human rights and its role in shaping the structure and rules of functioning of a democratic State. The separation of powers principle is articulated in Article 10 of the Constitution and in the State structures established by the Constitution and mechanisms provided for their functioning as well as constitutional values determining the limits of authority. Specifying the definition of constitutional democracy, the Constitutional Tribunal stressed that such system of government is characterized by the lack of the supreme organ of the State authority, while the principle of supremacy of constitution provides a foundation of the State. In the opinion of the Constitutional Tribunal, the separation of powers principle means that the legislative, executive and judicial branches of power are separated, and that there must be balance and cooperation between them. However, this principle has no merely organizational nature, since it is aimed at protection of human rights by preventing any branch of power from the abuse of its authority. The jurisprudence of the Tribunal gives us awareness that constitutional democracy consist in the limitation of power of the majority by the right of the individual. Of great significance, from the point of view of separation of powers in a democratic State, is the issue of relations between the legislative and executive powers. The parliamentary system established by the authors of the constitution in relation to these relations, is called by the doctrine 'rationalized parliamentarism'. The advantage of the legislative power is closely connected with the role given to statute by the authors of the constitution to guarantee the rights and freedoms of the individual. It seems that they even rely on statute and judicial power, rather than on the potential role of the separation of powers principle for protection of the individual against possible threats, particularly from the executive power.