The study investigates the moderating effect of CEO (Chief Executive Officer) duality and CEO ownership on the relationship between organisational slack and firm performance. Through reviewing relevant literature on organisational slack, agency and stewardship theories, this study develops hypotheses on the relationship between organisational slack and firm performance and the moderations of CEO duality and CEO ownership. On the basis of a large data of Chinese firms, this study finds that there is a positive relationship between organisational slack and firm performance, and the moderating effect of CEO duality is positive, whereas that of CEO ownership is insignificant. The findings not only improve the understanding on the performance implication of organisational slack but also indicates that stewardship theory is more powerful than agency theory in China. Copyright © 2013 John Wiley & Sons, Ltd.