Purpose In this research, a disaggregate analysis of road accident injury under-reporting in selected European countries is presented. Method The level of injury under-reporting is expressed by under-reporting coefficients, estimated as the actual estimated number of road accident injuries of a given severity to the number of related injuries recorded by the Police. These coefficients were calculated within national/regional studies in the examined countries, through a specially developed uniform methodology of linking and matching Police road accident records and hospital records. Log-rate models are developed in order to estimate the combined effects of country (CZ, FR, GR, HU, NL, ES and the UK), road user type (car occupant, motorcyclist, pedal cyclist, pedestrian), Police severity score (serious or slight injury) and MAIS score (the maximum Abbreviated Injury Scale score) on under-reporting. Results The results suggest that the examined characteristics have important combined effect on under-reporting (i.e. thirdorder interaction). The results of the analysis of lower-order interactions reveal specific particularities of each country/ region, indicating areas on which authorities should focus their efforts. Conclusions For example, it was found that slight injuries are more likely to be under-reported than serious injuries in the Czech Republic, France, and Greece, while the opposite is the case for the Netherlands and the UK. Moreover, although the Netherlands do not present high under-reporting rates overall, a particular issue is identified in this country for pedal cyclists’ slight injuries. Finally, a considerable part of total underreporting in most countries can be attributed to injury severity mis-reporting.