Cognitive mapping (CM) approach is reviewed, and the method is applied in analyzing an important case of societal decision-making. It is shown that CM is an effective way of representing argumentation, consequences, and the linkage between the concepts. The method integrates causal modelling and rational choice theory with parts of cognitive psychology. CM allows for a systematic arguing of issues. The decision-making problem described here concerns building a new nuclear power plant in Finland. There occurred strong proponents representing mainly the industry and technocratic and engineering experts, and an equally strong resistance represented by ordinary citizens, parliamentarians, and experts. The argumentation went ten years pro and cons before the parliament in 1993 decided against building the proposed nuclear power plant. It gives an ideal case to study the argumentation and contradictions there in as a whole by developing and applying a cognitive mapping approach. © 1995, Taylor & Francis Group, LLC. All rights reserved.