This study investigates how board size and occupational background of directors differentially influence social performance in for-profit and non-profit organizations. Using data from California hospitals, we develop a quantitative measure of social performance and provide the following empirical evidence. First, board size is negatively (positively) associated with social performance in for-profit (non-profit) hospitals. Second, the presence of government officials on the board is negatively (positively) related to social performance in for-profit (non-profit) hospitals. Third, representation of physicians on the board is (...) positively associated with social performance in for-profit hospitals, whereas their presence is not significantly related to social performance in non-profit hospitals. Our findings highlight the different effects of governance mechanisms on social performance in for-profit and non-profit organizations. (shrink)