This paper investigates the effectiveness of voluntary approaches in a comparative case study on European and Swiss climate legislation. Voluntary approaches are known to be less environmentally effective and economic efficient than other climate policy instruments but easier to implement and more acceptable for the business community. Voluntary approaches are preferred for approaching ‘new policy issues’ where more stringent policies and measures could hardly be implemented. However, they are known to dilute or postpone effective legislation. Moreover, voluntary agreements may impose a potential threat on competition due to the high level of collaboration of its signatories. This case study compares the voluntary accords signed by the European Automobile Manufacturers Association (ACEA) and the Association of Swiss car importers (ASIA) signed in 1998 and 2002, respectively. Whereas ACEA committed to decrease average CO2 emissions from new passenger to 140g/km, ASIA committed to reduce average fuel consumption to 6.4l/100km by 2008. Both agreements failed. Average emissions of new cars in Europe was still greater than 150g CO2/km, and average fuel consumption of newly imported cars to Switzerland was 7.1l/100km in this year. Our case study discusses the reasons for failure and assesses the effectiveness of voluntary agreements as climate policy instrument. Based on expert interviews with Swiss car importers and Swiss and German car experts, the achievements of the voluntary accords signed in Switzerland and the EU are compared. In Europe, stringent legislation had been postponed several times particularly due to political pressure of German premium car brands. In Switzerland, the majority of the interviewed firm representatives shows only low awareness of the motivation and purpose of the agreement and different understanding of responsibility.