  The single-site dynamical mean-field approximation is used to solve a model
of high-Tc cuprate superconductors which includes both d_{x^2-y^2} and
d_{3z^2-r^2} orbitals on the Cu as well as the relevant oxygen states. Both T
(with apical oxygen) and T' (without apical oxygen) crystal structures are
considered. In both phases, inclusion of the d_{3z^2-r^2} orbital is found to
broaden the range of stability of the charge transfer insulating phase. For
equal charge transfer energies and interaction strengths, the T' phase is found
to be less strongly correlated than the T phase. For both structures, d-d
excitons are found within the charge-transfer gap. However, for all physically
relevant dopings the Fermi surface is found to have only one sheet and the
admixture of d_{3z^2-r^2} into ground state wave function remains negligible
(<5%). Inclusion of the extra orbitals is found not to resolve the discrepancy
between computed and observed conductivity in the insulating state.
