The rotational structure associated with (X) over tilde (2) Pi(g) (000) ground ionic state of CO2+ has been investigated by threshold photoelectron spectroscopy and semiempirical calculations based on the distribution of Rydberg state levels at n = 2000. The calculations are in very good agreement with the rotationally resolved spectra for the (X) over tilde (2) Pi(g,3/2) and (X) over tilde (2) Pi(g,1/2) spin-orbit levels for both room temperature and supersonically cooled ground state CO2. Intensity anomalies are partly explained by decay mechanisms involving rotational and spin-orbit autoionization.