Preference votes constitute one of the key features of (open and flexible) PR-list electoral systems. In this article, we give an extensive overview of studies conducted on preference voting in Belgium and the Netherlands. After elaborating on the definition and delineation of preference voting, we scrutinize studies about which voters cast preference votes (demand side) and about which candidates obtain preference votes (supply side). For each of these aspects, both theoretical approaches and empirical results are discussed and compared. At the same time, we also pay attention to methodological issues in these kinds of studies. As such, this research overview reads as an ideal introduction to this topic which has repercussions on many other subfields of political science.