Metal silver nano-particles were deposited on the surface and in the pores of activated carbon by supercritical water impregnation (SCWI). Deposited silver particles distributed similar mean particle size as in particles on alpha-alumina support surface. Although the amount of particle deposition was relatively small compared to alpha-alumina due to large surface area of carbon support, the particle size distributions exhibited no significant difference. Extension of reaction time delivered smaller silver particles in uniform and well-dispersed conditions. Considerable numbers of silver particles smaller than 20 nm synthesized under longer reaction times were deposited inside the support pores without causing unintended particle aggregations. Results obtained in this work have emphasized the capability of supercritical water impregnation to porous supports as well as to hydrophobic materials offering promises to further applications besides catalyst preparation methods. (C) 2008 Elsevier B.V. All rights reserved.