The physical properties of Frohlich polarons and bipolarons are review
ed in relation to the recent experimental study of the mid-infrared ab
sorption spectra nf high-T-c cuprate superconductors, in particular, o
f Nd2CuO4-y, YBa2Cu3O6+x and La2CuO4+x. The spectral region studied is
of particular relevance for the open question of the presence of pola
rons and bipolarons in these materials, since it coincides with the fr
equency region where polaron and bipolaron absorption is to be expecte
d. In our view, the optical absorption spectra as observed in the dope
d cuprates are a manifestation of the polaron type relaxed excited fin
al states.