Oxygen-deficient YBa2Cu3Ox (Y123) exhibits persistent photoconductivity when illuminated by visible light. We have investigated resonant Raman spectra as a function of excitation wavelength and temperature, which shed new light on photoinduced effects and chain oxygen dynamics in Y123. Experimental evidence suggests that the mechanism behind the unusual photoinduced effects primary involves photoinduced oxygen ordering. Our Raman data also constitute the non-diffraction observations of the superstructure phase transition in Y123. (C) 2001 Elsevier Science B.V. All rights reserved.