This study analyses how linking emissions trading systems affects the economical aspects of climate policy at both national and international levels. The analysis focuses on cost-efficiency, distribution between participants, competitiveness and emissions targets. In addition we examine how linking affects the structure of emissions trading systems and decision-making. To analyse specific effects, we formulate a partial-equilibrium model to depict linking. With given assumptions, cost-efficiency of climate policy can be improved by linking local emissions trading systems and by switching from conventional credit-based systems to systems with “no lose” -targets, however the benefits are unevenly distributed between participants, inter alia, due to effects on competitiveness. Linking necessitates an international agreement on emissions levels between parties as linking changes the incentives to set an emissions target.