Quantitative aspects of surface concentration measurements of radiolabeled adsorbates by the thin-gap measuring technique developed by our group have been discussed recently by Poskus (see D. Poskus, J. Electroanal. Chem. 442 1998 5). It was argued that surface concentrations obtained by us were underdetermined since the backscattering factor of beta-radiation used in our work was too high versus a similar, but more recently obtained value by the quoted author. In response, we have reanalyzed our measuring conditions with a special emphasis on the backscattering phenomena involved in the experiment. Without contradicting the author's conclusions, the reported results indicate that the backscattering factor used in our formula linking radiation data and surface concentrations was correct, Apparently. in the scintillation-counter mode of the measurements, such a backscattering factor involves a simultaneous detection of reflected light from scintillation events and backscattered beta-radiation emitted by the radioactive preparate. Conversely, the Poskus measurements conducted by the use of a gaseous counter determine the second component only. Using a new, experimentally determined backscattering factor and a Au(111) electrode, we present a comparison between sulfate adsorption data obtained by the use of the thin-gap technique and Auger electron spectroscopy and prove, once again, the accuracy of our data.