Since the early 1990s, significant reductions of the NOx (Nitrogen Oxides) and PM (Particulate Matter) emissions from road transport have been observed, especially with Euro VI requirements, whereas current in-service freight vessels are still often equipped with diesel engines free of emission control. However, very few measurements on board freight waterways vessels have been carried out so far, due to both test difficulties and the poor accessibility and availability of commercial vessels. Indeed, only a few hours of emission monitoring could be performed from measurements on-board two freight vessels and a passenger boat, in the frame of a recent project. However, with the steady-state operating conditions observed most of the time, reliable functions could be set up to simply derive pollutant emissions from engine speed, respectively for each pollutant (CO2, NOx, PM and CO) and for each boat at various engine cruising speeds. Significant differences are observed between tested vessels, in terms of emissions factors expressed in g/tonne.km, for CO2, NOx and PM. Results in g/kWh are analysed as well and confronted with CCNR and European standards. The whole experimental emission factors from current waterways freighters are set against those from heavy-duty trucks. Comparisons are made with Euro II heavy-duty trucks which have similar engine manufacturing years and with the recent Euro V ones.