The partial photoionization cross sections for the four lowest-lying states of CO2+ have been measured with synchrotron radiation between 20 and 40 eV. The results are compared to previous photoemission measurements at discrete photon energies as well as fluorescence measurements using continuous radiation. The interrelation between photoemission and fluorescence data is discussed. The existence of four weak states of CO2+ with binding energies between 22 and 37 eV is verified. The dominant part of the photo-current at 40 eV is found to be associated with low-lying ionic states. © 1978 The American Physical Society.