Rhodamine‐B chloride (10 μM) has been used as a model plating additive in a study of the electrodeposition of Pb from , 0.5 and 5 mM Pb++ (pH 3) on Cu. Ellipsometer measurements during cyclic voltammetry have shown that the addition of dye results in a more compact bulk deposit than obtained in its absence. It also prevents complete monolayer coverage during formation of the Pb underpotential deposit and shifts the bulk deposition peak to more cathodic potentials during the first potential cycle. Dye effects on potential and micromorphology disappear during subsequent cycling, but reappear after relaxation periods at open circuit. Depletion and readsorption of dye on the surface have been confirmed by spectroscopic ellipsometry. Different optical film models have been investigated for the interpretation of spectroscopic ellipsometer measurements by use of multidimensional analysis.