This paper describes investigations on the role of electrolyte composition on the mechanism of the electroless copper deposition process. Both potentiostatic and galvanostatic polarization curves as well as steady-state plots are used in these investigations. Actual deposition rates are also measured through gravimetrically determined weight gain for comparison. The observation indicates that the two-compartment cell gives the mixed potential, E(m), values closer to that of the actual plating, whereas the deposition rate determined from the mixed current, i(m), value is lower than that of the actual one. The mechanism of electroless copper deposition changes from anodic to cathodic control as well as from diffusion to activation control depending on the concentration of Cu++ and HCHO. The mechanism in each case could be determined through the application of the Butler-Volmer equation to the half-cell reactions depending on the position of E(m) in the polarization plots of the individual half-cell reactions.