For the gamma‐ray satellite INTEGRAL, A 3‐D position‐sensitive imaging detector has been proposed. The instrument is based on a two layer CsI(Tl) device coupled with a coded aperture mask placed at ∼4 m from the detector. This particular configuration of discrete detection elements, together with the 3‐D position sensitivity will ensure good imaging capabilities throughout a large energy range from 40–50 keV up to ∼20–30 MeV. The imager will also have spectroscopy capability in the nuclear line region. In this work we present the first Monte‐Carlo simulation results regarding the reconstruction of the shadowgram of the mask pattern. A simulated image of a 511 keV Galactic Centre point source is presented for both the low and the high state.