This paper investigated the influences of Free Cash Flow, Tobin’s q, and Price-earnings ratio on the investment decisions by using North American monthly data from January 2000 to March 2017. Correlation Analysis and three Generalized Linear Models (GLM) are employed in this empirical research. The company size effect and within industry effect are controlled, and the reverse causality issue in the regression is considered. The reasons and implications of the strong cash flow/investment relationship are explored and discussed. Tobin’s q and cash flow/investment relationship are combined to identify the liquidity constraint and the over-investment of the free cash flow. Moreover, the CEO Pay Slice, which contains the CEO compensation information, are included in the regression model to investigate the impact of the CEO on the capital spending decision of the company.