International audienceThis article analyzes whether improving gender diversity in boardrooms improves firms' economic performance. In the context of French CAC40-listed companies between 2008 and 2012, this research uses instrumental variable panel regressions, including production frontier estimates, to arrive at two key results. First, gender diversity in boards depends on firms' attributes, including their previous gender promotion strategies. Second, promoting women in boardrooms has a significant and positive effect on economic performance, after accounting for the endogeneity of diversity. Gender diversity even reduces corporate inefficiencies and enables firms to come closer to their optimal performance