Silsesquioxanes (POSS) have recently become the subject of growing interest in many branches of materials chemistry. Despite this great interest, no direct metal-catalyzed method to cap the corner of the POSS molecules has yet been proposed. In this report, we present a highly efficient method for the synthesis of functionalized silsesquioxanes mediated by scandium(III) triflate, which opens up the possibility of introducing a wide variety of functional groups into this class of organosilicon compounds under mild conditions with excellent yields. We also investigated the differences in the activity of the Lewis acid (Sc(OTf)(3)) and the hidden Bronsted acid (TfOH) generated in situ from triflates as catalysts in the functionalization of silsesquioxanes. What is more, this solution provides an efficient corner-capping reaction and other functionaliztions to obtain silsesquioxane derivatives which are often not possible to synthesize with good yields, efficiency, and chemoselectivity using conventional method's.