The purpose of this paper is to investigate the relationship between the composition of boards of directors of Brazilian public companies and the firm value. The analysis is conducted by reference to a group of 208 Brazilian companies listed on Bovespa in the year 2008. The contribution of the study is done to assess the level of adherence to the recommendations of the Brazilian Institute of Corporate Governance (IBGC) regarding the composition of the board and its relation to market value. Using a multiple regression, three variables were studied: the level of board independence (Indep), accumulation of function by the Chief Executive Officer (CeoPowerful) and board size (Nmembros). The variable Nmembros was statistically significant, indicating positive correlation between corporate value and board size.