The importance of science as a tool of diplomacy continues to grow, particularly as an increasing number of challenges have a global dimension. Science has long had an international dimension and mjaor international research projects have sometimes needed diplomatic assistance to progress. However  ultimately science diplomacy is primarily about using science to advance the national interests of a country. As such science diplomacy has three major dimensions. First where the primary diplomatic objective is to directly promote  national needs through projecting a voice, influence, reputation or soft power - the objectives may vary according to country size and state of development. It may have security, economic and, trade, or national STI capacity building objectives. Secondly there are a number of bilateral or regional issues where science must be part of the relationship management - for example management of cross -boundary resources or environmental issues, agreeing standards, and crisis management. Thirdly there are issues where the national interest must be embedded within a commitment to the global interest - many of these are encapsulated within the sustainable development goals. The governance of ungoverned spaces - for example the Antarctic, the deep ocean. deep space and aspects of the cyber world all require science to be at the base of framing governance relationships. Yet while science is critical to all the sustainable development goals, their is no coordinated approach to identifying knowledge gaps and addressing them - this  may limit progress, The growing importance of science diplomacy is reflected in the number of countries appointing science advsiors to foreign ministries and seeking to better coordinate between international science activities and science diplomacy. A Foreign Ministries Science and Technology Advsiors network (FMSTAN) has been established to encourage interchange, skill development and sharing of approaches (www.ingsa.org)