This study explores the Clean Development Mechanism (CDM) which creates carbon credits from emission abatement projects in developing economies. The purpose of this paper is to examine the operation of the CDM with specific reference to fraud vulnerabilities regarding the additionality of a project. An examination of the process of establishment, certification and verification of additionality (confirmation that emissions post implementation of the CDM project are lower than those that would have occurred under the most plausible alternative scenario) is used to highlight the need for particular vigilance in respect to sustaining and improving the integrity of future market-based mechanisms post-Kyoto.