The corporate finance literature traditionally abounds in both theoretical discussion and empirical research concerning financing and long-term investment decisions. Managing short-term resources appears to be a much less remarkable issue, despite this resource's significant share of a firm's balance sheet and the time and effort required to manage the current assets and liabilities. This article provides insights into the relative importance of the selected working capital determinants from the European Union perspective. The determinants considered in the study include both external and internal factors, specifically the country in which a company operates, its industrial classification and the firm size. Using more than 10,000 aggregated observations from a sample of firms from 13 industries, 9 countries and 3 group sizes, covering the period 2000-2009, the findings provide evidence that corporate working capital is most affected by country-specific factors, followed by industrial factors and firm size.