  We study the electronic band-structure and transport properties of a
CuO2-plane within the three-band Hubbard model. The Dynamical Mean-Field Theory
(DMFT) is used to solve the many particle problem. The calculations show that
the optical gap Delta_opt is given by excitations from the lower Hubbard band
into the so called Zhang-Rice singlet band. The optical gap Delta_opt turns out
to be considerably smaller than the charge transfer energy Delta (Delta=ep-ed)
for a typical set of parameters, which is in agreement with experiment. For the
two-dimensional CuO2-plane we investigated the dependency of the shape of the
Fermi surface on the different hopping parameters t_CuO and t_OO. A value
t_OO/t_CuO >0$ leads to a Fermi surface surrounding the M point. An additional
different static shift of the oxygen energies is also considered to calculate
the electronic response due to a displacement of the oxygen atoms given by a
frozen phonon. The density-density correlation for the oxygen orbitals is
linear in doping for both hole and electron doping but shows a different
temperature dependency in the two regimes. In the first case it is temperature
independent and increases upon doping, which leads to an increasing
electron-phonon coupling for the B_1g-mode in high-Tc superconductors.
