Objective: ISPOR is the leading professional society for health economics and outcomes research (HEOR) globally. Recently, it launched its Women in HEOR Initiative, that aims to serve as a catalyst for women’s leadership in the field. Therefore, we were interested to find out how well ISPOR itself is doing in terms of gender diversity at their biggest conference. Methods: We used the conference programmes of ISPOR Europe conferences in 2016, 2017 and 2018 to assess the gender distribution of speakers that participated in issue panels and plenary sessions in these years. Results: 70% of all speakers (N=346) at 85 issue panels and plenary sessions during 2016, 2017, and 2018 were male. Almost one in three panels was all-male (a ‘manel’) and 64% of all panels had mostly male speakers (>50%). In contrast, only 11% of panels had <50% female speakers. Conclusion: Despite laudable effort to support the growth, development and contribution of women in HEOR through its Women in HEOR Initiative, females appear to be severely underrepresented at ISPOR’s biggest conference. ISPOR should make gender diversity a formal requirement for issue panel abstract submissions if it wants to advance women’s leadership in HEOR.