Submicrometric ceramic powders used as hardening agents for electrodeposited gold filmswere studied. Codeposits were obtained from a CN-free mixed electrolyte with or withoutthe addition of a brightening agent. Secondary ion mass spectrometry (SIMS) and scanningelectron microscopy (SEM) were applied to characterize the deposits. SIMS analysis gaveuseful information about the presence and distributions of additives in the films, and theinfluence of powders on metal-substrate interdiffusion phenomena were also shown. Surfacemorphology characteristics depending on experimental conditions, and the presence ofadditives were evidenced by SEM microscopy. Preliminary hardness tests were also carriedout to evaluate the effectiveness of additives as hardening agents.