AbstractThis paper analyses the effects of the mandatory adoption of International Financial Reporting Standards (IFRS) by Spanish listed companies in January 2005 on unconditional conservatism. The lack of robustness in previous evidence justifies analysis of this issue from a different perspective. To this end, we use, for the first time in this context, Ahmed and Duellman's (2007) methodology. These authors consider the impact of growth options and other future income, controlling for the idiosyncratic factors that the literature has found condition this type of conservatism. Additionally, beyond the pooled regression techniques usually used, we use econometric panel data techniques, which minimise the possible effect of endogeneity in the estimation of the proposed models. The results provide new evidence which supports our hypothesis that the adoption of IFRS has reduced the unconditional conservatism of Spanish listed companies.