GaN power devices allow building more compact power converters. In order to study these new devices, it is important to measure and estimate switching losses. Therefore, an instrumented PCB is developed including the measurement points needed for this purpose. The parasitic elements of the PCB layout extracted by ANSYS Q3D and the models of the measurement instruments are also included in the simulation model. In this way, by means of a validated model, it will be possible to evaluate the losses in an optimized circuit. Simulation and experimental results are presented to validate the simulation approach.