A photoactive polymer containing aryl substituted diazoketo groups was prepared by radical polymerization of methyl methacrylate, 2-hydroxyethyl methacrylate and photoactive 2-(2-diazo-3-oxo-3-(4-dimethylaminophenyl)-propionyloxy)-ethyl methacrylate. Upon UV irradiation at 365 nm, the diazoketo groups of the copolymer underwent the Wolff rearrangement and afforded ketenes that reacted with water to provide carboxylic moieties that could be removed by basic developer. It was demonstrated that this photoactive polymer could be used as a novel single component positive photoresist. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123: 554-561, 2012