In recent publications, the authors have shown that the exhaust gas fuel reforming technique has the potential to provide a way of controlling diesel engine exhaust emissions. The technology involves the incorporation of a reformer in the engine exhaust gas recirculation (EGR) loop. Fresh fuel is injected in the reactor, where it is reformed by catalytic reaction with exhaust gas. The produced hydrogen-rich gas is then fed back into the engine as reformed EGR (REGR). Thus, in this way, the engine in effect operates in dual fuel operation mode. In the present study, the particulate emissions of the diesel-hydrogen fueled engine were studied using an electrical low pressure impactor (ELPI). The work was performed by simulating the operation of an optimized engine-reformer system by feeding the engine with simulated reformate containing 24% hydrogen. The particle size and mass distribution were not affected significantly, but the particle total number and mass were reduced considerably, compared to the standard diesel fueling.