The performance of the heterogenous ideal absorbed solution theory (HIAST) using a uniform energy distribution and the global ideal adsorbed solution theory (IAST) is studied on their predictability f multicomponent adsorption equilibria along with experimental data of gases on two activated carbons. Results show that HIAST may not always provide better predictability than IAST if the energy distribution parameters are not properly chosen, although it is reported in the literature that in most cases HIAST is superior to IAST.