The emergence of peer to peer systems such as online auction websites is a major element in e-commerce yet relatively little is known about what influences its adoption and use in different parts of the world. Using an extended Technology Acceptance Model (TAM), user attitudes and behaviors from three national environmental contexts, Korea, Germany and New Zealand, are examined and compared to determine the factors influencing the adoption and usage of this system. The key questions this paper addresses are: Are there national differences affecting the ability for the TAM to predict OAWS acceptance, and if so, in what way? And are differences observed between heavy and light user motivations and perceptions of the medium and how these differ across national environments? Answers to these questions will increase the understanding for future marketers and developers of peer-to-peer systems. An extended TAM model was developed from which a number of hypothesized relationships are posited. We use the Davis, Bagozzi and Warshaw (1989) core TAM model extended by our arguing for two key influencing factors on a user’s attitude to using a new technology, perceived risk and computer affinity. We contend the drivers of perceived risk are: perceived enjoyment, trust in intermediary, perceived reputation system effectiveness, and positive past experience. Additionally we address the limited understanding in the literature of the national environment effects on technology acceptance. National cultural effects such as uncertainty avoidance and individualism, along with technological heritage and country innovativeness may need to be understood to determine potential differences in consumer activity and the robustness of the theoretical model. We also considered usage behavior to be important. Research for example, identifies heavy users as influencers on other potential adopters; thus important targets for developers and marketers of new technologies. Results suggest that although the core TAM is somewhat robust for the three nations along with the extended model for the respondents from South Korea, there are some key differences in the extended model between New Zealand and Germany. Specifically the relationships: Positive Past Experience and Perceived Risk are not supported in NZ or Germany, and “computer affinity” and “attitude to using” unsupported in Germany. We similarly found differences in the attitudes of light and heavy users between the samples, especially the Korean sample with the others. Our findings highlight that national environmental variations, especially between the “eastern” and “western” samples are important, which could be attributed to both uncertainty avoidance and individualism. Key conclusions and recommendations will be given.