The article contributes to the overall body of knowledge about investments made by small and medium-sized enterprises (SMEs) and their sources of financing. The author conducts an empirical research through a direct interview method on two samples: a sample of 1,001 microbusinesses (meaning those with up to nine employees) and a sample of 1,202 SMEs with 10 to 249 employees. The research shows that only 41 percent of Poland’s SMEs carried out investments in 2004. Investment indicators were the highest among medium-sized enterprises (74 percent), while microbusinesses showed the lowest indicators (41 percent). In the case of individual types of investments (day-to-day maintenance and modernization, purchase of computer hardware and software, purchase of individual machines and equipment, purchase of means of transportation, construction of new plants and purchase of turnkey production lines), the highest investment indicators were invariably recorded among medium-sized enterprises. The percentage of investing companies increased with an increase in employment. The same is true of the percentage of companies declaring investment plans for the next 12 months. Most of the companies polled used their own funds to finance their investments. An important (though usually only supportive) role in financing some investments (in particular, the purchases of means of transportation, turnkey production lines, machines and equipment) was played by loans and leasing. In analyses by market segment, the following rule was observed: companies with a higher level of employment displayed a greater tendency to use loans and leasing programs. Other sources of funds for investment projects in the SME sector were of marginal importance. Comparative analyses reveal that the use of external sources of funds to finance SME investment projects in Poland is usually two to three times lower than in other EU countries and the United States. However, no evidence of discrimination against SMEs in lending by banks was obtained. Only 2.5 percent of the companies polled have been refused bank loans over the past three years. An increased propensity to invest among Polish SMEs could be stimulated by appropriate activities of the government, banks and entrepreneurs themselves.