Despite the explosion of populism research, there is a shortage of comprehensive analyses of the ideational varieties of populist parties and of the different roles they play in contemporary party systems. In order to overcome such limitations, I provide a state-of-the-art review of the literature on the classification of populist parties and make three innovative contributions to populism research. First, by adopting a truly pan-European perspective to cover, in addition to EU member countries, contexts that are generally overlooked, including but not limited to Liechtenstein, Russia, Serbia and Ukraine, this review article provides an empirical application of the ideational approach to populism to 66 contemporary parties. Second, it highlights the major shortcomings of common approaches to the study of populist parties in contemporary party systems, which almost invariably treat them as ‘challengers’ or ‘outsiders’. Finally, it pushes the agenda further by providing a classification and empirical overview of the three interactive patterns characterizing the 66 populist parties under analysis: non-integration, negative integration and positive integration.