We address the effects imposed by localized interfacial states on the electronic structure of silicon nanocrystals embedded in ultrathin SiO2 films. The modeling used describes the charged interface defects through a delta(r) attractive potential within the effective mass approximation. The results show that the coupling among defect position,nanocrystal shape and effective mass tensor shifts the energy levels of the conduction band by tens of meV, causing dramatic changes to the overall nanocrystal electronic structure. (C) 2004 Elsevier B.V. All rights reserved.