International audience ; Distracted driving and, more specifically, the use of mobile phones, are increasingly seen as important issues for road safety. It is therefore needed to better evaluate its prevalence in order to be able to implement effective countermeasures. In this context, the Belgian Road Safety Institute has carried out in 2013 the first survey about handheld mobile phone use while driving at the Belgian level. We have implemented a rigorous and reproducible methodology based on, on one hand, a roadside survey on 126 locations, and, on the other hand, 6 days of observation from a moving car on highways. The survey allowed us to register the behaviour of 41 315 car, lorry, truck or bus drivers. Unlike many similar international studies, we only focused on drivers of moving vehicles. Beside mobile phone use, we observed other characteristics of the drivers and of their vehicle and tested their impact on the risk of mobile phone use by using a logistic model. The vehicle type and the road type are found both significant predictors of mobile phone use while driving. Overall, the results of this study show that handheld mobile phone use while driving is a problem in Belgium and allow identifying some measures against it. ; La distraction au volant et, en particulier, l’usage du téléphone portable sont de plus en plus considérés comme des problématiques importantes de sécurité routière. Il est nécessaire de mieux en évaluer l’ampleur afin de pouvoir prendre des contre‐mesures efficaces. Dans cette optique, l’Institut Belge pour la sécurité routière a mené en 2013 la première mesure de la prévalence du téléphone sans dispositif main libre au volant au niveau belge. Nous avons mis en place une méthodologie rigoureuse et reproductible basée, d’une part, sur des observations sur 126 sites en bord de route, et, d’autre part, sur 6 journées d’observation depuis un véhicule en circulation sur l’autoroute. L’étude a permis de relever les comportements de 41 315 conducteurs de voiture, camionnette, camion ou ...