The continuous increase of power density levels in components such as RF HEMTs or power LEDs and SiPs often leads to elevated hotspot temperatures that bring along reliability issues. Extracting and transferring the heat from the hotspot to the package and heatsink is however becoming increasingly difficult. One possible solution is the integration of materials with high thermal conductivity at package or board levels. Artificial diamond manufactured by chemical vapor deposition can have a thermal conductivity as high as 1800 W/m-K, a value 4.5 times higher than Cu. In this work we evaluate the potential of mounting several LEDs on diamond boards. To this end, the thermal profile of a 2×2 array of Cree XLamp XB-D LEDs mounted on MCPCBs and diamond boards was evaluated using Ansys. The impact of replacing the AlN die-carrier in the LED package with diamond was also evaluated. Due to the low thermal conductivity of the MCPCB dielectric layer, replacing the board with diamond has a larger impact than replacing the AlN die-carrier. The thermal benefit of diamond increases as thermal power density rises, either by increasing current levels or by bringing the LEDs closer to one another – even though replacing the MCPCB with a diamond board may induce thermal cross-talk between individual LEDs. By replacing both die-carrier and MCPCB with diamond, for 700 mA the aging of the LEDs slows down 79-97% depending on the activation energy of the failure mechanisms. Further benefit can be obtained by using die-attach, solders and thermal interface materials and solders with high thermal conductivity.