  An attempt to formulate the optical model of particle-hole-type excitations
(including giant resonances) is undertaken. The model is based on the
Bethe--Goldstone equation for the particle-hole Green function. This equation
involves a specific energy-dependent particle-hole interaction that is due to
virtual excitation of many-quasiparticle configurations and responsible for the
spreading effect. After energy averaging, this interaction involves an
imaginary part. The analogy between the single-quasiparticle and particle-hole
optical models is outlined.
