The role of excited states in affecting the transport of ionization energy in thermal plasmas in the temperature range 10,000 < or = T < or = 25,000 K is discussed by taking into account the dependence of diffusion cross sections on principal quantum number. The results show a strong effect at high pressure, while compensation effects reduce the role of excited states at atmospheric pressure. Extension of the results to nonequilibrium situations is discussed by presenting calculations of effective multicomponent diffusion coefficients. In this case also the presence of excited states dramatically affects these coefficients.