  We present an exact diagonalization study of the single particle spectral
function in the so-called t-t'-t''-J model in 2D. As a key result, we find that
unlike the `pure' t-J model, hole doping leads to a major reconstruction of the
quasiparticle band structure near (pi,0): whereas for the undoped system the
quasiparticle states near (pi,0) are deep below the top of the band at
(pi/2,pi/2), hole doping shifts these states up to E_F, resulting in extended
flat band regions close to E_F and around (pi,0). This strong doping-induced
deformation can be directly compared to angle resolved photoemission results on
Sr_2 Cu Cl_2 O_2, underdoped Bi2212 and optimally doped Bi2212. We propose the
interplay of long range hopping and decreasing spin correlations as the
mechanism of this deformation.
