This paper examines the passage of a new constitution in Ukraine in order to determine which factors contribute to the establishment of a stable separation of powers system at the national level. We focus on three types of factors: legacies of the past; the structure of institutions at key time periods; and the nature of dynamics between political groups. We find that while all of these factors play some role in the evolving institutional arrangements in Ukraine, negative legacies of the past can be overcome by the decisions of new political groups and the creation of new institutional arrangements.