The present study aimed to characterize the structure of nanocomposites obtained from the incorporation of three different polyhedral oligomeric silsesquioxane (POSS) in an epoxy resin. glycidylisobutyl-POSS, triglycidylisobutyl-POSS and glycidyl-POSS were added (5% by weight) in an epoxy matrix, diglycidyl ether of bisphenol-A (DGEBA), through a sonication process. The nanocomposites were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and dynamic mechanical analysis (DMA). The XRD analysis presented a characteristic peak of POSS. The incorporation of glycidylisobutyl-POSS showed a significant increase in the value of glass transition temperature (Tg), being also the most effective in terms of dispersion. It should also be noted that glycidyl-POSS presented a greater influence on the thermal stability.