  The p-d model which well describes the CuO_2 planes of the high-Tc
superconductors is studied by means of the Composite Operator Method (COM). The
relevant quasi-particle excitations are represented by composite operators. As
a result of taking into account spin excitations we find a p- like band near
the Fermi level. The dispersion of this band gives a Fermi surface which is in
good agreement with the experimental measurements. Due to the strong mixing of
the relevant excitations, the spectral weight of this band is reduced and gives
a large Fermi surface in the moderately doped region. The dependence of the
calculated physical quantities on model parameters, temperature and doping, is
in a very good agreement with the available Quantum Monte Carlo results.
