This research investigates the antecedents of social media advertising value, and the effect of this advertising value on online purchase intention in transitional economies in Southeast Asia. Moreover, the moderating effect of different types of social media on the relationships between the predictors and social media advertising value is also explored. The field study is conducted in Vietnam, a representative of Southeast Asian transitional economies in the current study. The results show that, in Southeast Asian transitional economies, the three social media advertising beliefs - i.e. informativeness, entertainment and credibility have positive effects on consumers' perceived value of social media advertising, which in turn positively influences their online purchase intention. Additionally, on social networking websites, the effects of advertising informativeness and entertainment on advertising value are weaker than those on content community websites. Nevertheless, there is no difference in the effect of advertising credibility on advertising value in both types of social media. Based on the findings presented, theoretical and managerial implications are drawn.