The EU launched its Emissions Trading Scheme (EU ETS) as a central pillar of European climate policy and envisages linking it with other ETSs. However, to what extent are linkages feasible? This work aims at examining some of the questions raised regarding linkage of the EU ETS with other regional or national emissions trading schemes by discussing: (i) the contribution of the EU ETS to the EU climate leadership; (ii) questions raised regarding the concept of linkage; (iii) the institutional, economic and political implications involved in linking. The EU and Swiss ETSs are taken as a case example.