As part of corporate governance theory, this article studies the relationship between the board of directors and the firm?s performance from the angle of the R&D investment level in the international context. Our model seeks to show if the R&D investment level acts as a mediating variable between the internal mechanism of corporate governance and performance. This effect is sensitive to the national systems of governance. This empirical study is based on a sample of 174 U.S. and 179 Japanese firms for the period 2008-2012. The results of the linear regressions conducted showing the relationship between, on the one hand, the internal administrator and the non-dual structure, and on the other hand, the firm?s performance, meditated by the firm?s R&D investment-level.