► We find that both board size and independent directors decrease bank performance. ► Gender diversity in the boardroom improves bank performance with caveats. ► Boards are relevant for banks with low market power, staggered boards and for small banks. We study whether board structure (board size, independence and gender diversity) in banks relates to performance. Using a broad panel of large US bank holding companies over the period 1997–2011, we find that both board size and independent directors decrease bank performance. Although gender diversity improves bank performance in the pre-Sarbanes-Oxley Act (SOX) period (1997–2002), the positive effect of gender diminishes in both the post-SOX (2003–2006) and the crisis periods (2007–2011). Finally, we show that board structure is particularly relevant for banks with low market power, if they are immune to the threat of external takeover and/or they are small. Our two-step system generalised method of moments estimation accounts for endogeneity concerns (simultaneity, reverse causality and unobserved heterogeneity). The findings are robust to a wide range of other sensitivity checks including alternative proxies for bank performance.