This paper examines the capital structure of listed firms in Poland, using firm-level panel data to study the determinants of leverage. Polish firms had extremely low leverage levels, suggesting a growing stock market and a potential reluctance of banks to grant loans to old and risky firms. The empirical exercise finds that large, new, foreign-owned firms, and firms with strong cash positions have higher levels of leverage. Finally, shareholder concentration has a neutral or even a beneficial influence on firm leverage. The nature of ownership may be primarily responsible for this finding.