The electrical low-pressure impactor (ELPI) is employed to measure the particle number and size distribution of the exhaust gas of internal combustion engines. If appropriate values of particle density are available, the emitted particle mass may be estimated with this method. For this work, three Euro3 passenger cars (one gasoline car operating under stoichiometric conditions, one diesel car, and one diesel car equipped with a diesel particulate filter, DPF) were tested on the New European Driving Cycle. The exhaust particles were measured using the current European regulations (gravimetrie method) and estimated from the ELPI particle number and size distribution. Different particle density values were used to estimate the particle mass using all ELPI stages or only some of them. The results show that the particle mass estimated with ELPI is quite well correlated with the mass collected on filters in the case of a Euro3 diesel passenger car without a diesel particulate filter; however, this method fails to estimate the particle mass emitted from gasoline or DPF-equipped diesel passenger cars.