Sectoral approaches are proposed as a means to broaden the global scope of greenhouse gas (GHG) mitigation to developing countries. Market mechanisms are put forward in that context to create incentives for mitigation in developing countries beyond the existing Clean Development Mechanism (CDM), and to encourage mitigation at least possible cost. The introduction of new, sector-based, market mechanisms is only one of many proposals discussed by UNFCCC Parties in the context of a post-2012 international climate policy framework, as a possible means to support mitigation actions in developing countries. This paper considers the carbon market aspects of sectoral approaches to reduce greenhouse gas (GHG) emissions in developing countries. It discusses three general ways to link sectoral goals with the carbon market: (i) intensity goals, based on a GHG performance per unit of output; (ii) fixed emission goals, with an ex-post issuance of credits or trading with an ex-ante allocation of allowances; and (iii) technology-based sectoral objectives. This paper explores the domestic policy implications of moving from a single project approach (i.e., CDM), to a multi-plant, sector-wide carbon market mechanism implied by sectoral crediting and trading. It also touches on possible transition issues, especially from intensity-based emission goals to fixed ones. The paper concludes that sector-based market mechanisms, regardless of the design option chosen, will require some significant upfront effort both nationally and internationally to set appropriate baselines and ensure adequate measurement, reporting and verification in order to generate economically valuable and environmentally-credible credits. Technology diffusion goals may be supported by other means than the carbon market if developing GHG baselines for such activities were too difficult. Sectoral approaches also imply some significant policy effort in countries that adhere to them, to ensure that the baselines are exceeded so that carbon market revenues are generated, and that these revenues represent effective incentives for entities to pursue GHG mitigation, wherever it is most cost-effective to do so.