A performance study was performed for CdZnTe coplanar grid (CPG) detectors when used as gamma-ray spectrometers. The detectors have the crystal volumes of 1, 1.6875 and 2.25 cm(3), respectively. Time stability of each CdZnTe CPG detector was investigated in a long-term operation (time span of 0.25 to about 100 h). The spectroscopic performances were measured at different bias voltages and at various photon energies ranging from 59.6 key (Am-241) to 1332.5 keV (Co-60) for each detector, and evaluated by using the following parameters: energy resolution in FWHM, peak tailing in peak-to-valley (P/V) ratio and in FWHM/FW.25 M ratio, and photofraction using the acquired gamma-ray spectra. No polarization effect was observed in terms of count rate, energy resolution and peak centroid shift. The obtained results indicate that better time stability and excellent spectroscopic performances of the present CdZnTe CPG detectors are shown for a room temperature gamma-ray spectroscopy. (C) 2012 Elsevier Ltd. All rights reserved.