For most of Western Europe, coalition formation is an important event after every election. The invention of game theory and behavioral scientific revolution in the social sciences in the second half of the XX century have inspired empirical work that is completely different from early government politics research. Political scientists have invented many models (theories) of coalition government formation in parliamentary democracies. But after the collapse of Soviet system many new democracies had spotted new challenges and difficulties with new experience of coalition politics. Most of countries in Central and Eastern Europe did not choose pure parliamentary mode of government but mixed one. In this field we consider to create a new model of coalition formation under specific circumstances of mixed regimes. We had investigated few cases such as Poland, Ukraine and Russia. And the main finding after comparison is as follow. In mixed-regimes with minority situation, where no party controls parliamentary majority itself, Head of State become the central figure in government coalition formation process. Moreover, during the first decade of XXI century in classic parliamentary systems Head of State more often influence coalition government process. In Belgium the King became one of the main actor of hard coalition bargaining in terms of long caretaker government. In Austria the Federal President control the political agenda and influence main political process. The next finding is that government coalition is more stable if president’s party controls more than half of coalition seats in legislature. In Ukraine loss of President''s party parliamentary control inevitably lead to political crisis. In Russia in mid-90s communist majority in parliamentary blocked many President''s initiatives. All new empirical material shows that coalition politics in mixed-regimes (e.g. semi-presidential, etc) need new exploration. And to find the answer to a new questions of coalition politics in new model of government formation for mixed regimes we might take in account not only size-principle or portfolio-allocation motivation, but head of state impact on coalition politics and his party power in parliament.
