  We calculate contributions of hadron resonances to two-photon exchange
effects in electron-proton scattering. In addition to the nucleon and P33
resonance, the following heavier resonances are included as intermediate states
in the two-photon exchange diagrams: D13, D33, P11, S11 and S31. We show that
the corrections due to the heavier resonances are smaller that the dominant
nucleon and P33 contributions. We also find that there is a partial
cancellation between the contributions from the spin 1/2 and spin 3/2
resonances, which results in a further suppression of their aggregate
two-photon exchange effect.
