The Conference of the Parties 9 in Milano, Italy (COP 9, 2003) approved modalities and procedures for afforestation and reforestation (A/R) project activities under the Clean Development Mechanism (CDM) of the Kyoto Protocol. According to the conclusions of COP 9, several approaches are available to monitor temporary carbon sequestration in A/R-CDM projects. Developing baselines for such monitoring is difficult because of a lack of basic growth and management data. In this paper, we present guidelines for preparing a project design document (PDD), in which growth and yield prediction in plantation forests plays an important role, and present a methodology for modeling and estimating carbon stocks using inventory data from Acacia mangium plantations in Malaysia and Indonesia.