In this paper we look at the way in which a wide range of interest groups have tried to influence political parties in Flanders. In order to test both aspects of the historic-institutional perspective and the rational choice perspective on party-group relations, we have analyzed the dissemination of in total 1569 memoranda by 616 interest groups over the six represented Flemish political parties in the 2013-2014 election year. We find that interest groups are very selective in the distribution of their memoranda to the different parties. Traditional parties seem more popular than new parties and political effectiveness seems to be the driver behind the selectivity of the large majority of the interest groups studied in this paper.