In this study, the electrochemical surface area (ESA) and specific activity are used to obtain a fair comparison of various activators used for electroless copper deposition (ECD). Different sizes (i.e., 27, 48, and 63nm) of Pd nanocubes (NCs) enclosed by {100} facets were successfully synthesized for use as new activators. The results of an analysis based on mixed potential theory indicated that the specific activities in terms of deposition current densities for the 27, 48, and 63nm NCs and 9nm nanoparticles (NPs) were 0.31, 1.06, 0.93, and 0.13mAcm −2 ESA , respectively. From the results of electrochemical quartz crystal microbalance measurements, the specific activities calculated from the mean deposition rates of the 27, 48, and 63nm NCs and 9nm NPs were 29.62, 68.72, 54.77, and 9.72μgcm −2 s −1 , respectively. A specific activity order of 48nm NC>63nm NC>27nm NC>9nm NP was obtained. The 48nm Pd NCs exhibited the maximum activity towards the activation of the ECD bath.