The market share of Gasoline Direct Injection (GDI) vehicles has been increasing, promoted by its positive contribution to the overall fleet fuel economy improvement. It has however been reported that this type of engine is emitting more ultrafine particles than the Euro 6c Particle Number (PN) limit of 6e11/km that will be introduced in Europe as of September 2017 in parallel with the Real Driving Emission (RDE) procedure. The emissions performance of a state-of-the-art GDI passenger car was measured, first in the original configuration without a Gasoline Particulate Filter (GPF) and then as a demonstrator with a coated GPF in the underfloor position. Regulated emissions were measured on the European regulatory test cycles NEDC and WLTC and in real-world conditions with Portable Emissions Measurement Systems (PEMS) according to the published European RDE procedure (Commission Regulation (EU) 2016/427 and 2016/646). Finally, tests were conducted on the chassis dyno to explore the impact on emissions of going towards the limits of the RDE boundary conditions (driving dynamics and ambient temperature). The results show that PN emissions of the state-of-the-art GDI vehicle were close to the Euro 6c limit in its original configuration without GPF. A maximum value of 9e11/km was measured during the on-road tests. However, PN emissions in that configuration increased to 2e12/km when going towards the RDE boundary conditions. With the GPF, PN emissions were controlled below the Euro 6c limit. A maximum of 4e11/km was observed near the tested RDE boundaries, demonstrating that the GPF enables real-wold PN emissions below a Conformity Factor of 1.0 under the conditions tested. No fuel penalty impact could be measured for the GPF during the tests and NOx emissions were always below the NOx Conformity Factor of 1.5 that will be effective with the Euro 6d stage from 2020 onwards.