In parliament, populist parties express their positions almost every day through voting. There is great diversity among them, for instance between left-wing and right-wing populist parties. This gives rise to the question: is the parliamentary behaviour of populists motivated by their populism or by their position on the left/right spectrum? This article compares the parliamentary voting behaviour of the Dutch SP and PVV, the only left-wing and right-wing populist parties that have been in a Western European parliament for more than four years. We find that for their voting behaviour the left/right position of these populist parties is more important than their shared populism. Only on one core populist issue (opposition to supranational institutions) do we find strong similarity in their voting behaviour.