Forested histosols have been found in some cases to be major, and in other cases minor, sources of the greenhouse gas nitrous oxide (N2O). In order to estimate the total national or global emissions of N2O from histosols, scaling or mapping parameters that can separate low- and high-emitting sites are needed, and should be included in soil databases. Based on interannual measurements of N2O emissions from drained forested histosols in Sweden, we found a strong negative relationship between N2O emissions and soil CN ratios (r2adj=0.96, mean annual N2O emission=ae(−b CN ratio)). The same equation could be used to estimate the N2O emissions from Finnish and German sites based on CN ratios in published data. We envisage that the correlation between N2O emissions and CN ratios could be used to scale N2O emissions from histosols determined at sampled sites to national levels. However, at low CN ratios (i.e. below 15–20) other parameters such as climate, pH and groundwater tables increase in importance as regulating factors affecting N2O emissions.