In order to explore the origin of the capacitance dispersion observed on solid electrodes, voltammetric and impedance measurements on single crystal gold electrodes have been carried out in the absence and presence of specifically adsorbed anions, mostly Br-. Evidence is presented showing that (i) in the absence of specific adsorption, the double layer on these electrodes behaves as an ideal capacitance (were the impedance approximated by a constant phase element, the exponent would be larger than 0.99); (ii) in the presence of specific adsorption, capacitance dispersion can be observed due to the sluggishness and/or diffusion control of the adsorption step, to the surface reconstnrction/deconstruction and to adlayer structural transformations.