In this paper the optoelectronic performance of selectively patterned conjugated polymers in light emitting diodes (LEDs) and photodetectors was examined. Polymers were patterned via a dry, non-reactive ion etching process using helium plasma. The polymers studied were the light-emitting poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) and poly[9,9-di-(2'-ethylhexyl)fluorenyl-2,7-diyl], and the conducting poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate). The electroluminescent spectra of etched and unetched LEDs are almost identical. There is no correlation between He-ion etching times and LED emission spectra changes. The MEH-PPV-based photodetectors show no decrease in external quantum efficiencies due to increased etch times. Results show that using helium plasma is effective at etching these polymers at predictable rates from selected areas without damaging the working device. (C) 2009 Elsevier B.V. All rights reserved.