The highly-resolved HeI photoelectron spectrum of CO2 is presented and its vibrational structure studied in detail. In the 2Πg ionic state the v3 antisymmetric mode is found to be excited in double quanta (v1- v2- v3 = 0. 0. 2) with energy hv3 = 181 meV. In the 2Σg+ state a single quantum of the same mode is found to be excited (hv3 = 189 meV) in combination with a v1 excitation. Vibronic interaction with vibrational levels in the 2Σu+ state of the ion is suggested to promote this (1, 0, 1) excitation. It is established that inelastic scattering processes contribute to the vibrational structure in the 2Σg+ band. The spin-orbit splitting in the 2Πg is determined to be 19±1 meV and 10±2 eV in the 2Πu state. Vibronic structure is resolved in the 2Πg band where the Renner-Teller coupling constant is determined to be ε = 0.21±0.02 and the vibrational energy of the v2 mode as 60±7 meV. In the 2Πu state the v2 energy is found to be hv2 = 60 meV from the observed hot-band structure.