In the age of digitalization, Public Relations (PR) practitioners tend to employ new/social media for event communication and promotion. PR academics, however, have yet to fully measure the efficacy of such employment. To tackle this issue, this study, applies Roger’s five-step adoption model as well as the Use & Gratification theory to an examination of roles that new/social media may play and factors that lead to the use of such media. Meanwhile, both audience’s and organization’s perspectives are invoked in the analysis. To this end, a particular event of 2015 CHINA (MACAU) International Automobile Exhibition is selected as a case for study. Methodologically, both quantitative (intercept survey, content analysis) and qualitative (in-depth interviews) methods are employed for data collection and analysis. Several interesting and important findings are found. First, new/social media prove to be effective channels in event communication and promotion by providing specifically more event-related information in an attractive and interactive way, in which the target audience NOT ONLY receive event information but become more likely to appreciate the information and subsequently are persuaded to participate in the event. Second, the target audience tend to perceive the information disseminated via new/social media as being more accessible, attention-commanding, understandable, interesting, believable, and memorable than traditional media, which entails an important implication for content generation in new/social media. Finally, the use of new/social media proves useful to organizations in building a long-term relationship with their audiences as it helps improve organization’s reputation effectively. iii Though preliminary, these findings, theoretically, help reconcile Roger’s five-step adoption model and U&G theory with the application of new/social media, and, practically, may encourage PR practitioners to rely more on new/social media in event promotion.