The photoelectron properties of DNA and RNA bases are studied using many-body perturbation theory within the GW approximation, together with a recently developed Lanczos-chain approach. Calculated vertical ionization potentials, electron affinities, and total density of states are in good agreement with experimental values and photoemission spectra. The convergence benchmark demonstrates the importance of using an optimal polarizability basis in the GW calculations. A detailed analysis of the role of exchange and correlation in both many-body and density-functional theory calculations shows that while self-energy corrections are strongly orbital-dependent, they nevertheless remain almost constant for states that share the same bonding character. Finally, we report on the inverse lifetimes ofDNAandRNAbases that are found to depend linearly on quasiparticle energies for all deep valence states. In general, our G(0)W(0)-Lanczos approach provides an efficient yet accurate and fully converged description of quasiparticle properties of five DNA and RNA bases.