The collapse of communism in Central, East and South-East Europe led to great hopes in the early 1990s. Three decades on, the initial optimism has given way to a mixed assessment: while the political transformation appears irreversible in some countries, a relapse to more authoritarian forms of government has occurred elsewhere. Similarly, the economic catch-up process takes much longer than originally anticipated. Many of the challenges might not be a legacy of state socialism but could be more deeply rooted. We provide an overview of where quantitative economic history research stands on the origins and persistence of this fundamental West-East-divide, focusing on the period before 1870 (by which time income differences were well established). Serfdom was proposed as an early answer. Non-agricultural explanations fall into three strands: demography, institutional weaknesses, and market access. We briefly discuss to what extent the factors identified here might have generated long-run stagnation in region.