Attosecond XUV FWM experiments on autoionizing Rydberg states of the polyatomic molecule, CO2, successfully generate wave-mixing emission signals that decay on ultrafast timescales. Although quantum beat oscillations indicative of the interference of multiple wavemixing pathways are present in the emission features, traces taken on-resonance of members of the Henning sharp series can be readily fit with single exponential decays, leading to measured decays on timescales of ten of femtoseconds. As described for similar background-free FWM measurements on autoionizing states of krypton and oxygen , the observed decays are equivalent to the excited state lifetimes in the absence of dephasing from interactions with other degrees of freedom. Table compares these experimentally measured lifetimes with calculated lifetimes of members of the Henning diffuse and Henning sharp series. The calculated lifetimes for the n = 6 -8 states of the Henning diffuse series range from 30 -90 fs while those for the n = 5 -7 states of the Henning sharp series decay on timescales over an order of magnitude longer in duration. Given the results of the lifetime calculations (Table ), the experimentally measured wave-mixing decays of 33 ± 6 fs, 53 ± 2 fs, and 94 ± 2 fs are consistent with the lifetimes of the Henning diffuse states, despite emission occurring at the energies of the Henning sharp series.