Party competition in Eastern Europe faces a seeming paradox. On the one hand, research finds increased political volatility in these countries, while, on the other, some authors demonstrate inherent ideological stability in the region. This research note presents a new methodological approach to adjudicating between these two findings, and suggests that while political organisations come and go, the ideological structure of party competition in Eastern Europe is strikingly steady. By developing a number of different measures of the dimensional structure of party competition, the consistency of the measures across countries, as well as their relative stability within countries over time, is demonstrated. The findings speak to current developments in Eastern Europe, and have implications beyond the region. The conclusion that even volatile party systems can be underpinned by stable ideological oppositions points to two different types of party system structure: one related to parties as organisations, and the other related to parties as expressions of political divides.