The partial C 1s Auger spectra of CO for a few vibrational components of the intermediate C(1s (1)) cation state have been obtained in photoelectron-Auger electron coincidence experiments. Then the measured coincidence Auger spectra have been used to simulate a complementary coincidence experiment in which the energy of the Auger electrons is fixed while the one of the photoelectron is scanned. The results show that the formation of the intermediate state and its decay are strongly linked and the coincidence Auger spectrum is dependent on the vibrational internal degree of freedom of the intermediate state. (C) 2008 Elsevier B. V. All rights reserved.