We determined the difference in carbon (C) stocks and C emissions between treated and untreated ponderosa pine stands over 100 years on the Apache and Sitgreaves National Forests, Arizona, USA, under assumed treatment scenarios, wildfire frequency, and annual percentage of area burned. Compared with the no-action scenario, total C stocks (live and dead biomass) were lower in the treatment scenarios because of timber removals from thinnings, whereas aboveground live C stocks were higher in the treatment scenarios. When total C stocks were used as the baseline, net present values (NPVs) of treatments were in the range of -$759.42 and -$722.58 ha1 if timber and reduced requirement for C in a buffer pool were assumed to be creditable, and NPVs increased significantly if C in wood products was also eligible for C credit. When aboveground live C stocks were chosen as the baseline, NPVs ranged from -$759.42 to $2,700.44 ha-1 with revenues from timber stumpage value, reduced buffer pool, and/or C in wood products. C emissions from simulated wildfires were lower in the two treatment scenarios than in the no-action scenario. The heavier thinning treatment resulted in lower C emissions from wildfires than with the lighter thinning treatment. © 2013 by the Society of American Foresters.