Successful implementation of policies and measures is key for effective climate legislation. In the political decision process, implementation depends to some extent on interest group influence. This project deals with the questions of why, how and what business interest groups lobby climate policy making in Switzerland and in the European Union. The public choice literature provides multiple reasons for organizations to become active as ‘institutional entrepreneurs’, based on rational behaviour. Firms may develop non-market strategies in order to dilute or postpone stringent legislation; or penalize competitors, e.g. by lobbying for ambitious technology standards. Voluntary approaches have become known as possible strategy for pre-emptive behaviour. One famous example, for Switzerland for instance, is the implementation of the climate cent in 2005, which successfully replaces the CO2 tax on transport fuels until present. The qualitative analysis deals with the positions of firms on climate policy. Document analysis of the consultation on the Swiss CO2 law in 2009 shows a pluralist picture of industry positions. We find that the business community is no solid block opposing climate legislation but a broad field of multiple positions including opponents and proponents to climate legislation. Economic sectors opposing climate legislation are oil and refineries, the heavy industries and road transport associations. Proponents of climate policy are renewable energies, forestry and timber production, finance and insurance, building services and manufacturing, and Swiss retailers. Peak business associations and road transport associations tend to overestimate the costs of climate policies and measures for their businesses. In the case of peak industry associations, this raises the question of appropriate representation of present and future members. Firms that are not owned by shareholders tend to show more environmental responsibility. The second part of the analysis compares the arguments provided in the consultation documents with the parliamentary discourse in Switzerland. We assess the degree of interest group representation as proxy for political power of business actors in political decision making. It turns out that peak industry associations, the Oil Union and road transport associations seem to have considerable influence on Swiss climate policy making. The results are combined with a social network analysis of the Swiss Parliament.