The accuracy of cross sections given by theoretical calculations is evaluated on the collision processes of molecular ions and electrons. The processes focused on are dissociative recombination, dissociative excitation, and rotational and vibrational transitions of the molecular ions of H2+, HeH+ , and their isotopes, which are relevant to divertor plasmas. Adopting the multichannel quantum defect theory, we calculated the state-selective cross sections for various states and energies. The validity of those calculations is investigated by comparing with experimental data under some limited conditions, and the calculations are verified from physical viewpoints.