The identification of ecosystem services (ES) and their valuation for potential use in environmental, social and political decision making is a fast growing research area. The ES literature is growing exponentially from less than 200 papers per year at the beginning of the Millennium to over 1600 per annum at the moment. While the ability to identify, classify and quantify ecosystem services has greatly improved and there is some movement towards unification of techniques, the hoped-for increased use in practical decision making has lagged severely behind. One reason for this is a slower integration of the resulting (ES) information with the type of multi-criteria decision support (MCDA) methods appropriate for issues with large numbers of criteria, both qualitative and quantitative, and large number of alternative options to be considered. The required techniques exist, (e.g. AHP, concordance, etc.) and are well known in the MCDA domain, but cross-fertilisation between the two scientific domains has been slow. This paper first summarises the established systems for classifying ecosystem services and then explores the issues relating to incorporating ES into a MCDA framework. When controversy arises and decisions are likely to be challenged, politically and legally, their underpinning by an accepted, rigorous and scientific methodology is important.