This paper investigates different thermal management solutions for GaN HEMT mounted on Printed Circuit Board (PCB) substrates. Wide bandgap (WBG) power semiconductors like GaN devices have the ability to operate at high switching-frequency (from few 100 kHz to several MHz). To take advantage of their high frequency switching capabilities, the parasitic inductances of power connections as well as the connections between the dies and the gate driver must be minimized. So the majority of GaN chips available on the market are packaged so that they can be directly attached to a PCB. The embedding technology of GaN dies in PCB substrate is attractive because it offers various interconnection possibilities. However, the low thermal conductivity of glass epoxy will result in high thermal resistance of the substrate. So it is of the first importance to seek technological means in order to improve the cooling of GaN chips soldered or embedded in such PCB structures.