The formation of spin polarons (spin-polarized clusters) in the weakly
doped antiferromagnetically ordered CuO2 planes of high-T-c cuprates
is investigated. The influence of additional holes is calculated withi
n a self-consistent mean-field approximation, by taking O-O hybridizat
ion (characterized by the parameter t) into account. It is shown that
the binding energy and the polarization of clusters strongly depend on
the value and the sign of t, i.e., a positive t promotes the spin pol
aron formation, while a negative t suppresses it. For the common value
t similar to 0.3 - 0.6 eV two polaron states with binding energies si
milar to 0.5 eV and similar to 0.3 eV are obtained.