Systematic measurements of resistivity and mobility at room temperature have been carried out on GaSe samples, doped with different iodine concentrations, in order to investigate the influence of iodine doping on the electrical properties of GaSe. To this purpose a series of GaSe single crystals have been grown by the iodine vapour transport technique in the same experimental conditions, with different iodine concentrations in the growth ampoule. By means of the Van der Pauw method, the electrical characteristics of some samples have been measured for each growth run, together with the behaviour of resistivity as a function of temperature. The results clearly indicate that GaSe, which undoped has a p-type conductivity, becomes a n-type semiconductor with the iodine introduction. The room temperature resistivity decrease and the carrier concentration increase at larger amounts of iodine. The conductivity is controlled by some donor levels lying at about 0.32, 0.5 and 0.62 eV from the conduction band, as it has been evidenced by ϱ(T) and TSC measurements.