This study examines the impact of board size of Australian firms on Tobinâs Q. Agency theory suggests that there is an inverse relationship between board size and Tobinâs Q (Yermack 1996; Eisenberg et al. 1998). The resource dependence argument, however, hypothesizes that larger boards can lead to higher performance as the CEOâs need for advice is a function of the complexity of the organization (Pfeffer 1972; Klein 1998). Analyzing a panel data of 1,530 firm-year observations using random effects technique, this study finds a positive relationship between board size and Tobinâs Q. The random effects regression results also reveal that the positive relationship between board size and Tobinâs Q is driven by firm size as this positive relationship is only found in larger firm sample but not in the smaller firm sample. The overall results support the resource dependence argument.