In the increasingly digitalized societies of the 21st century, online political participation is on the rise and will probably challenge the importance of traditional forms of political participation. Political scientists, however, are still struggling with the conceptualization and the measurement of online political participation. Is online political participation really a new form of political participation or does it only take place in a new space and make use of new means? How can we measure online political participation, especially in internationally comparative surveys? Is survey-based research on online political participation necessary given that we can directly extract behavioral data from the web? Against the backdrop of these open questions, the paper has two major goals. It will provide an overview over the current debates on the conceptualization and measurement of online political participation, and it will develop some guidelines on how to measure online political participation in surveys. Thus, in a first step existing conceptualizations and measures will be reviewed. The discussion will especially focus on the relation between online participation and traditional forms of political participation and what this means for issues of measurement. In a second step, building on this review, we will test different measures of online participation by conducting a survey experiment (between-subjects design, open-access online panel). The results of this test will provide guidelines for future survey measures of online political participation.