To effectively respond to the development and changes in information technology, it is important to understand the process by which information technology diffuses among firms. Existing studies have been able to identify the diffusion process of information technology among organizational members, organizational structural factors that promote the internalization of information technology within organizations, and the communication media used by organizational members in the technology adoption process, but they have not comprehensively elucidated the diffusion process of information technology across organizations. To overcome these limitations of prior research, this study conducted a specialized survey of 64 publicly listed firms regarding the diffusion processes of local area networks (LANs) and relational databases. The objectives of this study were threefold: first, to identify the influence that firms already using information technology exert on firms intending to adopt information technology; second, to examine differences between early adopter and late adopter organizations in terms of organizational structural factors and the time required for information technology adoption, as well as the importance of communication media used at the planning and adoption stages of information technology; and third, to empirically investigate performance differences between early and late adopter organizations. The survey results indicated that firms intending to adopt information technology were not influenced by firms that had already adopted it. Significant differences were found between early and late adopter organizations in variables such as top management age, top management's interest in information technology, degree of formalization, degree of centralization, reward systems, the IT manager's attitude toward change, time required for IT adoption, and IT utilization performance. Additionally, interpersonal media were used more than mass media at both the IT planning and adoption stages. This study provides useful guidelines for establishing IT adoption strategies for firms and IT diffusion strategies for vendors.