Even though Prime Ministers (PMs) are the central actors in parliamentary democracies, little comparative research aims to explain their performance in office. As heads of party governments, they have a variety of different responsibilities. Among others, these include managing a cabinet of ministers, providing stimulus and direction for domestic policy development, brokering between different societal interests, reacting to unexpected events and serving as the chief spokesman of government, both at national and international level. In this paper, we explore whether certain PMs handle these tasks better than others. For that purpose, we make use of a unique data set covering 131 cabinets in eleven Central and Eastern European countries between 1990 and 2018. We define performance as a two-dimensional set of tasks, which PMs ought to fulfil: firstly, the tasks delegated to their office such as leading the cabinet and directing domestic affairs and, secondly, providing accountability to parliament and their own party, who constitute the direct principals. A comprehensive expert survey covering twenty respondents per country allows us to assess the quality of prime-ministerial performance in each cabinet empirically. Starting from the assumption that broad and long-standing political involvement provides individuals with experience enhancing their likelihood to fulfil their tasks as PM successfully, we study the impact of the type of political office and the time served in each function before becoming head of government to explain variation in performance both across and within countries. More concretely, we argue that heads of government who served in multiple positions in local and national politics, such as ministers, legislators, and party leaders, have the necessary know-how to succeed in office. Political outsiders, in turn, which have no first-hand experience about the functioning of cabinets, policy-making, international politics, parliaments, and parties, are least likely to perform successfully. In addition, we examine how differing institutional, political and socioeconomic contexts cause variation in prime-ministerial performance and moderate the effect of political experience. Our analyses thus reveal how different career patterns affect the performance of PMs in Central and Eastern Europe.