The objective of the present work is to investigate the performance of a single PEM electrolytic cell by carrying out electrochemical impedance spectroscopy measurements (EIS) coupled with polarization curves. Electrochemical impedance spectroscopy is a powerful non-destructive method to individuate the origins of the several polarization processes affecting the cell performance. In combination with other characterization methods such as polarization curves, EIS allows to distinguish several phenomena happening inside an electrolytic cell on the basis of the different relaxation times of each single process. Furthermore, it helps to quantify their impact on the efficiency and durability of the membrane electrode assembly (MEA).