Science and technology diplomacy has become an important policy agenda because of its diplomatic utility and enhancing of international science networks. However, different countries possess different objectives and governance of S&T diplomacy. In this context, this paper seeks to answer the following questions: what are the similarities and differences of S&T diplomacy in countries and what shapes these characteristics? To answer these questions, this paper conducts a comparative case study with five countries - Switzerland, Germany, Japan, the United Kingdom, and the United States - whose S&T diplomatic programs are highly recognized and benchmarked by other countries. A useful typology is devised to conduct a systematic comparison. For S&T diplomatic objectives, this paper suggests five types by elaborating concepts from the previous literature: access diplomacy, promotion diplomacy, public aid diplomacy, functional diplomacy, and global leadership diplomacy. Also, in terms of a governance model for S&T diplomacy, three models - a sciencecentered model, a science-outsourcing model and a top-down coordinating model - are suggested based on leadership organization. This paper reveals the different characteristics of the selected countries in S&T diplomacy. While the selected countries pursue almost every type of S&T diplomatic objective, the US and the UK tend to conduct influence-based diplomacy more than other countries do. In addition, different countries each have unique governance models for S&T diplomacy. While more research is necessary for vigorously testing the causes of different objectives and their relationship with governance models, this paper suggests more general policy implications throughout. The strength of the country's S&T base is fundamentally important for the success of S&T diplomacy. However, domestic S&T assets need to be transferred to its diplomatic capabilities. In this sense, the appropriate governance that fits best with the country's S&T mission should be established, while S&T communities should increasingly play a leadership role in evolving global S&T networks.