Electrochemical surface areas (ESAs) were used to estimate the specific activities of different-sized Ag nanoplates (NPLs), which were used as novel catalysts for electroless copper deposition (ECD). Based on the consideration of ESAs and deposition kinetics measured using an electrochemical quartz crystal microbalance, the mean specific activities of NPLs with sizes of 74 nm, 117 nm, and 162 nm were determined to be 0.107, 0.250, and 1.017 mg . cm(-2), respectively. The largest NPLs showed the highest activity. Simultaneously, in the Tafel plot normalized to the ESA, the specific current density corresponding to 74 nm < 117 nm < 162 nm NPLs for formaldehyde oxidation in the high overpotential region was determined. This anodic reaction activated with various NPLs could thus be the rate-determining step in ECD. Additionally, an untypical open circuit potential curve containing two mixed potentials for two period depositions-Cu deposition on Ag NPLs and Cu on the deposited Cu layer-was observed. In the intended application, conductive Cu patterns on a flexible polyimide film using Ag NPL ink of 2.5 wt% solid content were successfully fabricated by inkjet printing combined with catalyzed ECD. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.025209jes] All rights reserved.