The effect of Ag decoration on the gas sensing characteristics of SnO(2) nanowire (NW) networks was investigated. The Ag layers with thicknesses of 5-50 nm were uniformly coated on the surface of SnO(2) NWs via e-beam evaporation, which were converted into isolated or continuous configurations of Ag islands by heat treatment at 450 °C for 2 h. The SnO(2) NWs decorated by isolated Ag nano-islands displayed a 3.7-fold enhancement in gas response to 100 ppm C(2)H(5)OH at 450 °C compared to pristine SnO(2) NWs. In contrast, as the Ag decoration layers became continuous, the response to C(2)H(5)OH decreased significantly. The enhancement and deterioration of the C(2)H(5)OH sensing characteristics by the introduction of the Ag decoration layer were strongly governed by the morphological configurations of the Ag catalysts on SnO(2) NWs and their sensitization mechanism.