The diffusion of social media such as Facebook or Twitter opens up entirely new opportunities for International Organizations (IOs) to directly communicate with and engage an increasingly aware and assertive public. The paper theorizes respective communication activities along three dimensions of social media use: adoption, intensity and dialogical responsiveness. Using Twitter, Facebook, and other data on a stratified-random sample of 50 IOs, event history analysis is employed to examine the determinants of "digital diplomacy" along these three dimensions. Results suggest that multiple factors shape the application of social media tools for public communication purposes: first, increased pressures on IOs for self-legitimation facing politicization, second, IO mandates for pro-actively inducing social change on the ground, third, new demands for IO accountability by enhancing institutional transparency.
