Abstract This work is about the analysis of reliability issues in pulsed power resonant converters, which feature fairly unique operational characteristics, differentiating them substantially from more common power electronics applications (e.g., inverters, dc–dc converters). First, an overview of the converter functioning is provided; then, an a priori minimisation of the electro-thermal stress levels affecting the active switches (IGBTs) is searched for: this is based on an experimental parametric study of the turn-off snubber and of the DC-link capacitance value for which the overall switching power losses can be minimised. Accurate measurements of the switching losses in the IGBT modules are performed by means of a calorimetric technique. Finally, infra-red measurements of the IGBTs surface temperature during transient operation are presented, showing that the introduction of soft-switching strongly reduces the amplitude of lower frequency thermal cycles.