This working paper takes a comparative snapshot of social media use in and by OECD governments. The focus is on government institutions, as opposed to personalities, and how they manage to capture the opportunities of new social media platforms to deliver better public services and to create more open policy processes. The analysis is based on a large amount of empirical data, including a survey of OECD governments on policies and objectives in this area. Major challenges are discussed, notably those related to the uncertainty of institutions on how to best leverage social media beyond “corporate” communications. The paper proposes tools to guide decision makers: a checklist of issues to be considered by government institutions, a set of potential indicators to appraise impacts, and a range of options for more in-depth policy analysis.