This study was conducted to verify the power of opinion leaders for information diffusion on online brand communities and participation in companies' product development process and it consisted of two sub-studies. Study 1 was to develop a scale to verify online brand community members' community participation to classify them into different types. Study 2 was to verify the difference between general consumers and these members, who play central roles in the degree and range of information diffusion according to their type of participation and the process of information diffusion in relation to their activities and brand attachment.For the purpose of these two sub-studies, this study gathered data of the members of a consumer-led automobile brand community on a leading portal site in Korea. In result of the analysis, participation in brand communities was classified into four types based on six factors: “self-centered observers”, “passive participants”, “passionate participants”, and “simple subscribers”. Among these types, “passionate participants” were the opinion leaders in brand communities and very active in information diffusion, brand attachment, and co-production intension. On the other hand, “passive participants” and “self-centered observers” had different motivation for active participation in brand communities compared to “passionate participants.” The findings of this study would greatly contribute to studying consumers' sub-cultures and consumer behaviors in the virtual environment. Also, companies could use these findings to consider ways to use online brand communities as strategic tools for brand development and efficient management.