The aim of this study was to ascertain the possible presence of an isomorphic process between the annual and sustainability reports of mining companies, analysing the extent to which the amount of information disclosed is similar. To this end, the instrument established by Sampaio et al. (2012) was used, which includes four groups of indicators in line with the procedures established by the Brazilian accounting standard T-15 and other recommendations from the Ethos and IBASE Institutes, as well as the guidelines established by the Global Reporting Initiative (GRI) for the preparation of annual and sustainability reports. Ten annual and sustainability reports were analysed in a period comprising two different years - 2009 and 2012. The definition of these years took into account the study carried out by Sampaio et al. (2012), in order to allow a comparative analysis of the findings of the previous study with the present study.The mean and standard deviation were used as parameters to support the treatment of the data.The results showed an increase in the volume of social and environmental information.