In the past, green taxation has become a widespread tool in pollution control in Europe. This new type of state intervention is based on an idea developed by environmental economists and diffused internationally through various channels of information exchange. We argue that the idea itself does not inform us about the way in which green taxation is designed because sectoral policy networks influence power relations, which in turn influence the actual design of green tax schemes. Thus, policy networks are the intervening variable explaining why an internationally diffused policy idea is implemented differently in various national settings. This argument is supported by a comparison of pesticide taxation and CO2 taxation in Denmark, Norway and Sweden.