In this article, we address the problem of measuring professionalism of political campaigns in European parliamentary elections. We use a comparative research design with party-level campaign data from two fairly similar EU member states, Germany and Finland, and two elections, 2004 and 2009. Theoretically, our analysis is based on the so-called party-centred theory of professionalism, which puts an emphasis on party characteristics in explaining the variance of campaign professionalism. We hypothesize that besides observing increasing party-level campaign professionalism in time and higher levels of professional campaigning in Germany, professionalism is positively associated with a party’s size, its right-wing orientation and recent change of leadership. We found support for the time-effect and party size, whereas evidence in country comparison, ideological orientation and change of leadership was inconclusive, suggesting significant differences among countries and elections. It also seems that the political left harbours the most professional parties. This calls for a re-evaluation of the party-centred theory of campaign professionalism.