Over 500 delegates took part in the third international ECSA conference in September 2020. Across 30 sessions, as well as keynote talks, e-poster presentations and more informal settings, they discussed and debated a diverse range of subjects related to citizen science. This special edition of ‘JCOM’ brings together some of the central themes that were under the spotlight at ECSA 2020. Since ECSA 2020 has been one of the first examples of a conference that moved completely online, and it has been considered a big success, we also include the Conference Report, as supplementary material with this editorial.

Citizen science is a transdisciplinary approach that responds to the current science policy agenda: in terms of supporting open science, and by using a range of science communication instruments. In particular, it opens up scientific research processes by involving citizens at different phases; this also creates a range of opportunities for science communication to happen This article explores methodological and practical characteristics of citizen science as a form of science communication by examining three case studies that took different approaches to citizens' participation in science. Through these, it becomes clear that communication in citizen science is ‘÷always’ science communication and an essential part of “doing science”.