In the field of voting behavior research, substantial attention has been paid to the relation between information and the capacity of individuals to make political decisions that are in their own best interest. The purpose of this paper is to further investigate the relationship between, on one side, political knowledge and heuristics, and on the other side, what I will call "attitude congruent" voting - i.e., voting for the party/candidate that best matches one's own existing policy attitudes. I will test if this relation holds across a large number of countries while taking into consideration the possible direct and mediating role of institutional characteristics. Using the data from the European Election Survey 2009, an operationalization of attitude congruence based on ideological proximity and propensity to vote is computed. The empirical analysis does not find any support to confirm the positive impact of political knowledge, thus contradicting previous expectations. On the other hand, a simple heuristic such as party ID, has a small but positive impact on “attitude congruent” voting, pointing to the fact that heuristics could be more important than political knowledge for the quality of electoral decisions. Much more, institutional characteristics such as: party system volatility, polarization, the number of parties, government stability and the age of democracy do play a substantial impact on how “attitude congruent” voting varies across countries.