We formulate a relativistic bound-state calculation of the decay of η (0−+) mesons into two gluons or two photons. The decays of ηc, ηc’, ηb, and ηb’ are calculated and a value of αs deduced from the total width of ηc. The calculated value for ηc→2γ is in agreement with experiment. The decays of η→2γ and η’→2γ are calculated and by comparison with experiment and the bound on ι→2γ, restrictions are placed on the Xη, Yη, Xη’, and Yη’ mixing coefficients of Rosner. The comparison with the Schrödinger-equation calculations shows that the inclusion of relativistic propagators spreads out the annihilations so that they do not occur at r=0. This suppresses the 2S and higher-level decays, with the greatest suppression for the lightest quarks.