Science communication has shifted considerably in Europe over the last decades. In the theoretical realm, one-way information has been replaced by models of science communication that stress public engagement and public participation in science and technology. Dialogue seems to have become a communication target on its own, beside such things as public understanding or awareness of science. This article articulates different notions of science communication and explores to what extent they can coexist in practice by presenting an empirical analysis of a public event on cancer genomics. The event brought together cancer patients, scientists and (para)medical professionals. Data on the intended and actual communication at the event were collected by document-based research, interviews, observation of communication processes and a written questionnaire. The results show that the event proved to be successful in terms of creating awareness and understanding of cancer genomics research and its implications for diagnosis and treatment of cancer. The results also illustrate that despite the intentions of those organising public communication activities, achieving the ideal of a two-way public dialogue in practice is not self-evident. This is partly due to a lack of commitment to societal issues at the institutional as well as the (inter)personal level. Drawing from our experiences and literature, we suggest that in science communication literature the role of dialogue moderators is underexposed. We argue that in doing and evaluating science communication, analytical attention should be focused on the interaction among the public(s) and invited experts and the opportunities for empowering both for decision-making in their everyday lives.