The localisation of the discharge channel under the conditions of a glow discharge in air, at different distances from the cathode and at various points in the cathode dark space for different voltages, has been studied by measuring the radial distribution of the light intensity in the discharge channel. It has been shown that the radial ion distribution which has a flat maximum at lower voltages changes over into an approximately Gaussian one as the discharge voltage is increased. In the former case the width of the flat maximum decreases as the ion-channel proceeds towards the cathode. At higher voltages (~ 6 kV.) the flat maximum type of distribution in the ion-channel progressively changes over into the Gaussian as the channel approaches the cathode.