Hollow core-shell Pt-Ag nanoparticles (NPs) with discontinuous Ag shells were successfully synthesized using a Pt-seed-mediated growth method and used to catalyze electroless copper deposition (ECD). The activities and resulting ECD kinetics of hollow NPs and solid-core Pt-Ag NPs with sizes of 5.9, 9.6, 14.7, and 20.6 nm were compared. The deposition kinetics was investigated using an electrochemical quartz crystal microbalance (EQCM). The induction period for the 7.3 nm hollow NPs, as observed using a potential-deposition time curve, was 5 s, significantly shorter than that of the 5.9 nm solid Pt-Ag NPs (13 s). At a deposition time of 500 s, the mean mass activities in terms of the weight of the catalyst for the hollow NPs and 5.9 nm NPs were determined to be 4.591 and 3.065, respectively. The large hollow NPs with discontinuous Ag shells show a 1.5-fold higher mass activity than that of the 5.9 nm NPs. In a careful comparison based on the same electrochemical surface area (ESA), the specific activities were in the order: hollow NPs > 20.6 nm NPs > 6 nm NPs > 14.7 nm NPs > 9.6 nm NPs, where the hollow NPs show faster deposition (5.88 x 10(-9) g m(-2)s(-1)) than the 20.6 nm NPs (5.2 x 10(-9) g m(-2) s(-1)).