SnO 2 :m mol% CoO (0.5 ≤ m ≤ 6.0) ceramic specimens were studied by impedance spectroscopy in the 5 Hz-13 MHz frequency range during heating cold-pressed specimens from room temperature to 1250°C. The electrical resistivity during sintering decreases from 4 to 6 orders of magnitude in the 400-1500 K temperature range depending on the amount of CoO. An increase in electrical resistivity in the 570-670 K range is related to the release of adsorbed water. The results for the 970-1500 K show that the higher the amount of the CoO addition, the lower is the temperature at which SnO 2 :CoO reaches a minimum electrical resistivity. This suggests that oxygen point defects created by dissolution of cobalt ions in the SnO 2 lattice are controlling the densification rate of these ceramics.