Corporate governance literature argues that board diversity is potentially positively related to firm performance. This study examines the relationship in the case of women in top executive jobs and on boards of directors. We use data for the 2500 largest Danish firms observed during the period 1993-­2001 and find that the proportion of women in top management jobs tends to have positive effects on firm performance, even after controlling for numerous characteristics of the firm and direction of causality. The results show that the positive effects of women in top management depend on the qualifications of female top managers.