It is well known that different types of electoral systems create different incentives to cultivate a personal vote and that there may be variation in intra-party competition within an electoral system. This article demonstrates that flexible list systems - where voters can choose to cast a vote for the list as ordered by the party or express preference votes for candidates - create another type of variation in personal vote-seeking incentives within the system. This variation arises because the flexibility of party-in-a-district lists results from voters' actual inclination to use preference votes and the formal weight of preference votes in changing the original list order. Hypotheses are tested which are linked to this logic for the case of Belgium, where party-in-a-district constituencies vary in their use of preference votes and the electoral reform of 2001 adds interesting institutional variation in the formal impact of preference votes on intra-party seat allocation. Since formal rules grant Belgian MPs considerable leeway in terms of bill initiation, personal vote-seeking strategies are inferred by examining the use of legislative activity as signalling tool in the period between 1999 and 2007. The results establish that personal vote-seeking incentives vary with the extent to which voters use preference votes and that this variable interacts with the weight of preference votes as defined by institutional rules. In addition, the article confirms the effect of intra-party competition on personal vote-seeking incentives and illustrates that such incentives can underlie the initiation of private members bills in a European parliamentary system. ; DFG ; Gottlieb Daimler - and Karl-Benz-Foundation