This study examines the relationship between corporate governance ratings and firm performance, including
both a global measure of corporate governance and four sub-indices corresponding Audit, Board Structure,
Shareholder Rights and Compensation, provided by Institutional Shareholder Services (ISS). The corporate
governance ratings represent a proper approximation of the quality of corporate governance practices from inside
the companies. This fact determines the investors which seek to hold shares in certain companies for a long term
to be interested in the quality of corporate governance practices related to those companies. Using the
cross-sectional multiple linear regression model for a random sample of 155 U.S. companies listed at New York
Stock Exchange, NASDAQ and NYSE Amex Equities, belonging to twenty industries, in 2011, our research
emphasizes a negative relationship between corporate governance global rating and firm performance. Also, we
find a negative relationship between corporate governance sub-indices and firm performance, with some
exceptions. However, when we removed the companies from financial and real estate sectors, respectively 29
companies, resulting another sample of 126 companies, the results support the same findings. This study reveals
that the commercial corporate governance ratings, like Governance Risk Indicators (GRId), provided by
Institutional Shareholder Services (ISS) are affected by measurement errors. This research is important to the
shareholders and investors globally, who are using commercial corporate governance ratings, in order to identify
and quantify the risks of their investments. Our study suggests that shareholders and investors should not base
entirely on commercial corporate governance ratings in their investment decisions, because they couldn’t take
the proper investment decision each time.