The objective of this paper is twofold. Primarily, it aims at measuring the degree of compliance to the International Accounting Standard of the Italian listed groups. Secondly, it is intended to capture to what extent the level of harmony in financial reporting practice has increased after the introduction of IAS/IFRS, since differences in practice could still exist in the application of IFRS. Compliance and harmonization will be measured with regard to the valuation of the participating interests in subsidiaries, in associates, in joint venture, and minority interests. The data source is the consolidated financial statements for the period subsequent to the introduction of IAS/IFRS (2005-2008). Previously, Italian listed companies presented their consolidated financial statements in accordance with domestic GAAP. In order to measure the level of compliance to IAS / IFRS, and harmonization in the accounting choices for the Italian firms, the H index developed by van der Tas (1988) has been applied with the purpose to find out whether, and to what extent, compliance and harmonization have been achieved after the mandatory introduction of the new accounting requirements.