This paper mainly focused on the comparison of nanoparticle size distribution and number concentration level characteristics with gasoline and diesel fueled light duty vehicles. In the engine research, particle size distribution and number concentrations were analyzed by a DMS500 with engine parameters. Time-resolved particle number concentration levels from test vehicles were measured by a golden particle measurement system (GPMS) as recommended by a Particle Measurement Programme (PMP) on certification modes such as New European Driving Cycle (NEDC), Federal Test Procedure (FTP)-75, and Highway Fuel Economy Test (HWFET). In addition, particle emission characteristics from vehicles were analyzed by DMS500 during transient and high-speed driving conditions. From the results, we found that the formation of particles was highly dependent on vehicle speed and load conditions for each mode. The diesel vehicle equipped with a particulate filter showed substantial reduction of the total particle number whose number concentration was equivalent to that of the gasoline vehicle. The nucleation mode particles from gasoline fuel were mainly emitted; however, the accumulation mode particles from the diesel fuel were generally analyzed.