We calculated frequency-dependent first hyperpolarizabilities for electro-optic Pockels effect, β(ω; 0, ω), in π-conjugated molecules containing azomethine bonds using the CNDO/S-CI sum-over-states method. First, we examined the dependence of static β on formulas for the two-center Coulomb integral, γAB. The choice of the γAB formula has little effect on the relative β value, but a considerable effect on the absolute value. Then we investigated the relationship between the magnitude of β(ω; 0, ω) and the donor/acceptor substitution sites. We found that the molecule with no donors or acceptors can be divided into donor and acceptor regions whose existence causes the donor/acceptor site-dependence of β(ω; 0, ω).