The adsorption of anions on highly ordered (111)-type gold electrodes with and without Cu adatoms in perchloric and sulfuric acid electrolyte solutions was investigated on an electrochemical quartz crystal microbalance. A distinct increase in mass due to the specific adsorption of hydrated bisulfate and perchlorate anions was observed in Cu2+ -free solutions and their amounts were determined as a function of the potential. The composition of the Cu-adlayer (theta(Cu) and theta(anion), coverages of Cu adatoms and co-adsorbed anions) during formation or removal in the potential sweep was also determined in both electrolyte solutions. A pair of reversible anodic and cathodic peaks in the voltammogram for the first Cu-upd region in H2SO4 was found to correspond well to the reversible changes in theta(Cu) and theta(anion). In contrast, asymmetric features of the voltammograms for the second Cu-upd region in H2SO4 and for whole processes in HClO4 corresponded to the large hysteresis in changes of theta(Cu) and theta(anion), probably originating from a slow rearrangement of both species.