The article looks at how the financial condition of companies influences their investment policies. To estimate the significance of individual financial indicators, the authors used data from the balance sheets and profit and loss accounts of more than 58,000 non-financial Polish firms from the 1995-2010 period. The Generalized Method of Moments (GMM) was used for the estimations. The model described in the article involves estimates of individual, sectoral and time effects. It indirectly takes into account the cost of capital in the investment equation. The cost of capital is a variable that is extremely difficult to observe at the level of individual companies, the authors say. The analysis was conducted for different groups of companies arranged by size. On the basis of the estimated econometric models, the authors validated a hypothesis about a significant influence of financial ratios on companies’ investment rates. An improvement in the cash flow has the greatest contribution to the investment rate, the authors say, and this effect is strongest in the case of small companies. While analyzing the impact of the cash flow on the investment rate, the authors confirmed the strong non-linearity of the trend for all groups of enterprises. In addition, they found that the financial pressure felt by companies in the form of debt and costs of interest reduces the level of investment. In the context of the monetary policy transmission mechanism, this may point to the existence of interest rate and balance sheet channels, the authors say. Another conclusion from the research is that financial pressure increases the probability of the financial accelerator mechanism – or a situation in which adverse shocks to the economy may be amplified by worsening financial market conditions. In the estimated model, small businesses turned out to be far more sensitive in their investment policies to an economic downturn than the corporate sector as a whole. The financial condition of enterprises reflected by selected indicators clearly influences the investment decisions of individual companies, and sensitivity to these indicators in terms of investment additionally depends on company size. This is important for assessing the mechanism whereby monetary policy is transmitted to the small and medium-sized enterprise (SME) sector, the authors say.