European-wide standard methodologies for rock fall hazard assessment and mapping would constitute a very important step towards more transparent and reproducible procedures used for these purposes, and would provide as well a higher uniformity in land use planning and risk management. However, the current situation in Europe shows the opposite tendency, as the mapping methodologies are far from being possibly harmonised, due to two issues: the differences in the national guidelines and those concerning the the way the hazard is quantified. This paper is mainly focused on the second problem, and analyses some practical difficulties to account for when trying to compare and harmonise methodologies for rockfall hazard mapping. Three hazard mapping methods based on rock fall trajectory modelling are compared, developed according to the Swiss, Andorran and French guidelines. The methods are applied at a Swiss site, following one given set of guidelines, and are based on the results obtained by the same trajectory simulation code, in order to show the dependency of the results strictly on the mapping techniques.