This paper analyzes the impact of auditing on the quality of accounting information of firms. Based on a sample of 237 firms listed in Spanish capital markets in 2002 and 2003, our study has two different scopes: the characteristics of the auditing committee and the relation of the firm with auditors. Our results show a close relation between the independence of the auditing committee and the quality of accounting information and, to a lesser extent, a positive impact of the size of the committee on the reliability of financial statements. In addition, we find that the reputation of the external auditor improves the quality of financial statement and that there is an experience effect related to the duration of the contract with the auditor.