Motivated by the European Union (EU) decision to mandate application of the International Financial Reporting Standards (IFRS) to the consolidated financial statements of all EU listed firms (Regulation (EC) 1606/2002), starting in December 2005, we compare the value relevance of accounting information in 14 European countries in the year prior to and the year of the mandatory adoption of the IFRS. We focus on three accounting information items for which measurements under IFRS are likely to differ considerably from measurements under domestic accounting practices across the EU countries prior to the introduction of the international standards: goodwill, research and development expenses (R&D), and asset revaluation. These three items, selected on an a priori basis, have been shown in previous research to differ in the effect of uncertainty on their future benefits. We use valuation models that include these three variables and in addition the book value of equity and earnings. Overall, our study suggests that the adoption of the IFRS has increased the value relevance of the three accounting numbers for investors in equity securities in the EU. Association tests support our two hypotheses: (1) in the year prior to the mandatory adoption of the IFRS, the incremental value relevance to investors of the three domestic GAAP-based accounting items was greater in countries where the respective domestic standards were more compatible with the IFRS; and (2) the higher the deviation of the three domestic GAAP-based accounting items from their corresponding IFRS values, the greater the incremental value relevance to investors from the switch to IFRS. These associations prevail when considering cross-country differences in the institutional environments, which tend to provide complementary effects.