The policy instrument of greenhouse gas (GHG) emissions trading has gained prominence since the early 2000s. At the end of 2016, 21 distinct GHG emissions trading systems (ETS), covering 35 countries were operating worldwide (ICAP 2017). China has announced the launch of a national ETS for the second half of 2017, which is expected to become the world’s largest carbon market. A number of other countries and subnational jurisdictions such as Thailand and Mexico are considering the adoption of a GHG ETS. Hence, it is increasingly important to improve our knowledge about the forces that shape the initiation, design and functioning of such systems, be they internal or external to the jurisdictions. This Special Issue aims to contribute to improving our knowledge and understanding of the expanding turn to greenhouse gas emissions trading. In particular, it aims to investigate the role and specificities of diffusion processes in the emergence of various GHG ETS globally, with a particular focus on the interaction between external influences and domestic dynamics within jurisdictions that newly design and adopt a GHG ETS.