In this paper multi-chip LED modules with aluminum nitride (AlN) Al and aluminum oxide (Al2O3) based substrates were successfully designed fabricated and investigated Finite element method (FEM) and electrical test method were used to evaluate the thermal performance of LED modules Both simulation and experimental results show that the module with AlN based substrate exhibits better thermal performances than the two others Moreover AlN-based substrate LED module shows the best optical performances The optical performances of the LED modules with different substrates not only verify that the optical output and degradation of LED has a direct relation with the input current but also show that the degradation could begin earlier if the thermal dissipation is not managed well Crown Copyright (C) 2010 Published by Elsevier Ltd All rights reserved