Companies should be interested in implementing corporate social responsibility (CSR) practices not only for ethical reasons, but also for their potential profits. Considering the need to confirm this relationship more thoroughly, this research is based on the only stock market index in Spain which is an objective indicator of best business practices. The purpose of this study is to find out whether being listed in the FTSE4Good IBEX explains a different ulterior financial performance. To this end, the potential accounting and stock market differences between two groups of companies listed in the Spanish IBEX are analysed: those classified as responsible due to their inclusion in the responsible company index and those companies which, as they are not in it, do not receive this denomination. The study, conducted according to the CSR strategic approach, covers 2008–2013. Its outcomes confirm the presence of significant differences between the two groups. Copyright © 2017 John Wiley & Sons, Ltd and ERP Environment