The behavior of a cyanoalkaline copper plating system was studied with a special focus on the role of two organic additives, cetylpyridinium chloride (CPC) and poly(ethylene glycol) Mw 1500 (PEG). The influence of these additives on the adsorption behavior of the CN- ligands released during the Cu(I) complex reduction process has been investigated. Spectroelectrochemical results obtained by in situ Raman spectroscopy were complemented with cyclic voltammetric measurements. The potential-dependent surface-enhanced Raman spectroscopy spectra showed two prominent features at ca. 2090 and 2040 cm(-1), within the Raman shift range typical of C equivalent to N stretching v(CN-). Using a double- Gaussian model, a numerical elaboration of the two v(CN-) d bands was done, estimating the potential-dependent values of the (i) peak position, (ii) peak intensity, and (iii) full-width at half-maximum. Our results show (i) a chemical interaction of CPC with adsorbed CN-, weakening the Cu-CN- adsorption bond, (ii) an interaction of PEG with the Cu surface giving rise to cathode-blocking and alteration of the Cu growth mode. (c) 2005 The Electrochemical Society. All rights reserved.