Many researchers who study ‘citizen science’ implicitly or explicitly engage in comparative research by relating and contrasting concepts of citizenship, science, and citizen science. In this webinar, we jointly explore these and related concepts with researchers of citizen science (social scientists and life scientists), sensitizing ourselves to what exactly is being compared and how, and why comparison is useful. We will consider what ‘citizen science’ covers in terms of a range of practices, ideas, and cases and why it is presently such a fashionable science policy and research term. We also ask how the concept acquires various meanings in various contexts; whether and how ‘citizen science’ travels across various boundaries (geographical, cultural, linguistic, political, typological, scientific); and how we might engage with it differently, among other questions. Our interest in these issues arises from a recurring field observation made across cultures and contexts: citizen science researchers and other citizen science stakeholders (e.g., credentialed scientists, policymakers) often have lengthy discussions about how to properly define citizen science. While these discussions can be fruitful, they involve a reductive understanding of what citizen science is – or can be. Social scientific renderings of ‘citizen science’ as a heterogeneous practice consisting of “many modes” help to open up this discussion (Strasser et al 2018). However, if citizen science is conceived of too broadly, can anything meaningfully be said about citizen science at all? Presenters and participants are asked to explore these considerations by drawing on their own research experiences, with the aim of developing fruitful comparative research avenues into ‘citizen science’ and comparative research more generally. Strasser BJ, Baudry J, Marh D, Sanchez G, Tancoigne E (2018) “Citizen science”? Rethinking science and public participation. Sci Technol Studies 32(2):52–76.