The transient shielding performances of small transparent cubic boxes illuminated by an impulsive plane wave, exciting the frequency range up to several gigahertz, are analyzed by applying an 3D full wave method. The box is made by transparent polycarbonate walls coated with a thin nanostructured transparent film, consisting of alternating thin layers of metal (Ag) and dielectric (TiO2) materials, and contains a total of 68 nm of silver. A GNP-based nanocomposite absorber, custom designed and tuned on the first resonance frequency of the enclosure is used to panel the inside of the box in order to dump unwanted reflections. © 2012 IEEE.