The purpose of this research is to study what issues may affect investor adoption of on-line trading in the Hong Kong financial market. The studied system is a system that provides straight-through trading for investors, rather than an order routing system that forwards orders from a broker firm to the appropriate market. This paper focuses on feasibility of changing to a new service or system in the social/organizational perspective by using existing models. In particular, the Decomposed Version Theory of Planned Behavior (DTPB) is used to identify the factors that affect investors’ adoption of on-line trading. A hypothesized model is developed as a basis to design a questionnaire to test the model. A correlation analysis is performed to investigate whether the hypothesized attributes, variables, and belief structure are correlated with each other. After such analysis, the factors that influence the adoption of the proposed system are identified, as well as the relationships between the factors. Such results can be helpful to the Stock Exchange of Hong Kong (SEHK) and the Hong Kong Securities and Futures Commission (SFC) for their planning the launch of Internet trading.