Forest expansion into formerly agricultural land plays a relevant role for generating carbon sinks eligible under afforestation activities in the Kyoto Protocol (KP) carbon accounting framework. This paper provides a methodological framework for the multi-temporal assessment of carbon accumulated in these new forest stands, at the reference years of the KP commitment periods: remote sensing analyses, integrating optical imagery and airborne laser scanning data with field survey, are combined with the carbon simulation model CO2FIX to project carbon changes. The approach is applied to a case study in the central Apennines (Italy) to assess the carbon sink associated to these new forests at the years 2008, 2012 and 2020. The approach is based on forest cover change detection and growing stock mapping, while the multi-temporal carbon sink analysis is performed by means of the CO2FIX model. In the considered test area, the results highlight a compound annual rate of forest expansion equal to 0.26% for the period 1990-2012. The overall carbon stored by the new stands is 21.1Mgha-1 (relative standard error less than 10%) at the year 2012, projected to reach 33.5Mgha-1 at the year 2020.