Transparent conducting Ga-doped zinc oxide (GZO) thin films (150 nm thick) were sputter-deposited on glass substrate at room temperature. As-deposited GZO films were wet-patterned with weak organic acid aqueous solutions containing formic or citric acid. Wet etching behaviors of the films were influenced by the type and concentration of organic acids used. The concentrations of formic and citric acids were varied from 0.02-0.1 and 0.0008-0.02 M, respectively. The concentration-dependent different etching behaviors, i.e., diffusion-vs reaction-limited etching modes, were observed for each etchant. Different rate-limiting behaviors were also verified by the calculated activation energy data for vertical etching of the films as a function of concentration of each etchant. With the optimal etching conditions for the GZO films on glass substrate, the wet patterning of the films deposited on poly(ethylene terephthalate) was also attempted. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3429217] All rights reserved.