Introduction: The negative effect of female gender identity on participation at face-to-face academic conferences for delegates, speakers, chairs and panellists has previously been reported. Little is known about how ethnicity may affect conference participation, or about how gender and ethnicity intersect. To our knowledge, this is the first study describing conference participation by both ethnicity and gender in panellists and delegates, and the first to describe this within a hybrid conference setting. Methods: We collaborated with the European AIDS Clinical Society (EACS), the organisers of the 18th European AIDS Conference, a large, 3223 delegate, hybrid conference held online and in London, over four days in October 2021. During the conference, we observed the number and type of questions asked at 12 of 69 sessions and described characteristics of the panel composition by ethnicity, gender and seniority. A post-conference survey of conference attendees collated demographic information, number of questions asked during the conference and the reasons for not asking questions. Results: Men asked the most questions and were more likely to ask multiple questions in the observed sessions (61.5%). People from White ethnic groups asked >95% of the questions in the observed sessions. The fewest questions were asked in the sessions with the least diverse panels in terms of both ethnicity and gender. Barriers to asking questions differed between genders and ethnicities. Conclusions: Improvement in access and participation at medical conferences is needed. Our study aims to raise awareness and provide evidence to help improve equality, diversity and inclusion in the professional medical conference setting and support equitable dissemination and sharing of knowledge. Intersections of gender and ethnicity shape inequality and need to be examined in combination. Further work is needed to evaluate the role of other social identities. We recommend future work takes such intersectionality into account and that conference organisers strive for diversity on panels to improve education and engagement of delegates.