In this work, several spectral techniques such as pulsed and steady-state photo-ionization spectroscopy, deep level transient spectroscopy and infra-red steady-state photoluminescence spectroscopy have been combined to reveal and clarify the prevailing defects in cadmium zinc telluride (CZT) materials and device structures. The room temperature measurements were routinely performed to correspond with operation conditions of the CZT devices. The spectra recorded by the contactless and contact techniques have been compared to clarify the role of defects residing in bulk and near-contact regions. Keywords: CdZnTe, radiation detectors, pulsed and steady-state photo-ionization spectroscopy, deep level transient spectroscopy, infrared photo-luminescence spectroscopy, defects