The partial oxidation (POx) reforming of Ultra Low Sulphur-Diesel (ULSD), rapeseed methyl ester (RME) - biodiesel and Fischer-Tropsch synthetic diesel fuels (SD) were studied by using a fixed-bed reactor. The ease of reforming the three fuels was first examined at different O/C feed ratios at constant gas hourly space velocity (GHSV) of 35 k h(-1) over a prototype monolith catalyst (1%Rh/CeO2-ZrO2). The hydrocarbon species (C-1-C-6) produced in the reformer were analyzed using direct gas injection gas chromatography mass spectrometry (GC-MS). Under the same O/C ratios for 35 k h(-1) the fuels conversion and process efficiency was dependent on the fuel type, and followed the general trend: SD > biodiesel > ULSD. The GC-MS analysis shows that both, biodiesel and ULSD diesel produced significantly higher amounts of alkenes compared to SD fuel. Fuel with relatively high aromatics content such diesel can be efficiently reformed to syngas over the catalyst used in this study but the reformer operating range (e.g. O/C ratio and space velocity) is limited compared to paraffinic fuels such as FT-SD. At increased GHSV of 45 k h(-1) and O/C = 1.75, the diesel fuel conversion efficiency to syngas (H-2 and CO) was improved significantly and the formation of intermediate species such as methane, ethylene, and propylene was reduced considerably as a result of the increased peak reaction temperatures. The reduced HC species and increased H-2 concentration in the reactor product gas from the reforming of FT-SD fuel can provide significant advantages to the IC engine applications. (C) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.