there is a world trend to reinforce the regulation of financial markets and of public sector enterprises, as a means to protect the interests of the principal. one way to reduce investor exposure is to improve corporate governance practices in businesses which use public funds. this article analyses the following questions in the light of the agency theory: will best corporate government practices protect investors? are there differences in the short and long term? does regulation designed to improve corporate government help to improve and capital structure? in the long- and short-term in the mexican financial market, and globalization, privileged information and convergence between mexican businesses and their foreign counterparts seem to have an influence on risk and yield.