This article analyzes the influence of the sources of motivation that lead companies to adopt environmental management systems (EMSs) on the outcomes of these systems. A set of hypotheses derived from an extensive review of the literature is analyzed using cluster analysis – in order to identify groups of companies – as well as correlation and regression analyses, with data obtained from a survey of 361 Spanish organizations that have environmental certification. The results reveal that, for the groups identified, companies from the holistic cluster (with high levels of both internal and external drivers) and from the internal focus cluster (with more intensive internal sources of motivation) secure greater benefits from the process of adopting an EMS. This article also sheds light on the influence on the outcomes of some variables that have been under‐researched, such as the economic resources invested in an EMS and whether or not the certified companies belong to a sector with high environmental pressure. The findings help to characterize the firms with environmental certification and may also help managers, policy makers and other stakeholders to anticipate the potential benefits of EMSs. Copyright © 2015 John Wiley & Sons, Ltd and ERP Environment