Discerning which sources contribute most to differences in per capita carbon emissions and why presents a daunting task for analysts, since several underlying factors affect emissions from hundreds of end-uses. This paper provides derails of an international comparison methodology and carries our the comparison on a number of international Energy Agency (IEA) member countries. These calculations show where differences in the components of emissions lead to large gaps among countries. The data, from national sources, are the most extensive and disaggregated ever compiled for this kind of international analysis. Overall, activity differences account for the largest part of the gap in per capita emissions among IEA countries. If we normalize emissions to GDP, then transport activity levels, energy intensities, and utility carbon intensity share about equally in explaining the differences in carbon/GDP ratios among countries. Most of the structural variations arise in the freight, services, and household sectors-sectors less sensitive to international competition than manufacturing.