SUMMARY
Based on the new institutional economics, the focus of this research was to identify transaction costs in CDM (Clean Development Mechanism) projects and investigate whether they affect project efficiency or create project development barriers. More specifically, this study analyzed the variables that could affect the differences between estimated emissions reduction of CDM projects and the actual reductions obtained (Reduction Success - RS) after the project has been implemented and monitored, verifying if agricultural projects are more or less efficient. Most projects do not show satisfactory performance in terms of RS, even though most achieve more than 91% RS. The most efficient sectors in the world are HFC and N2O (in Brazil, N2O and fossil fuel), and the least efficient sectors are solid waste and agriculture (in Brazil, agriculture and solid waste). Finally, this study concludes that transaction costs affect the success of CDM reductions, the most relevant being ex-ante costs resulting from information gaps and measurement problems.