  We analyze the spectral density of a single level quantum dot coupled to
superconducting leads focusing on the Andreev states appearing within the
superconducting gap. We use two complementary approaches: the numerical
renormalization group and the Hartree-Fock approximation. Our results show the
existence of up to four bound states within the gap when the ground state is a
spin doublet (\pi\ phase). Furthermore the results demonstrate the reliability
of the mean field description within this phase. This is understood from a
complete correspondence that can be established between the exact and the mean
field quasiparticle excitation spectrum
