The article studies populist regimes, their relationship with authoritarianism and democracy and modes of their transformation. First, the approaches to conceptualizing populism are critically analyzed; second, the concepts are systematized through the maneuvering on the ladder of abstraction; third, the ways of classifying populist regimes are studied, and fourth, the influence of populism on political regime change is assessed. The authors made an attempt of radial categorization of populism having distinguished its central and peripheral features. On the basis of the minimalist definition of populism by C. Mudde “the idea” revealing itself in the antiestablishment and will of the people discourse, was taken as a central category. Such approach allowed to distinguish three species of populism including ideational, personalist and charismatic, thus making the categorization applicable for comparative research. The conceptualization of populist regimes was reviewed. It is noted that populist regime is rarely conceptualized as a separate type of political regime and is more often associated with personalist regime or as a sub-type of democratic regime. The further development of the B.G. Peters and J. Pierre’s approach led to conclude that populism is a regime modification, inherent in all types if political regimes. Democratic and hybrid regimes are more inclined to such regime modification, that is why the populist regimes evolve multidirectionally.The study concludes that the establishment of populist regime in polities at different levels of political development – from consolidated democracies to premobilized authoritarian and democratic systems – leads to differentiation of functions. In the former cases populist regimes foster the redetermination of the effectiveness criteria for ruling elites and democratic governance in general, and in the latter – populist regimes support the general framework of the in-country political process by filling the institutional gaps.