This article describes the benefits of implementing an environmental management system (EMS) conforming to the ISO 14001 standard in Polish companies. Experience shows that implementing an environmental management system in a company can bring a number of benefits, not only for the company itself but also to the whole surrounding environment. Prevention of pollution, which is the idea underlying the concept of an environmental management system, generates mechanisms aimed at minimizing material, resource and energy consumption. It is difficult to identify the benefits which directly arise from environmental management system implementation, as well as the benefits which indirectly spring from maintaining the system. The following article is an attempt to classify the benefits gained according to a number of factors. These factors are related to operational activities and management in an organization. Moreover, some notable benefits that improve the state of natural environment are described in this article. The following article can inform many organizations about the benefits of implementing environmental management system compliant with ISO 14001 standard and convince them to implement such a system. Moreover, thanks to this article some groups of benefits resulting from implementing, maintaining and continually improving an environmental management system will be pinpointed. The survey presented in this article was conducted out in 700 companies that have certified their environmental management systems at ISO 14001 standard.