  The evolution of central stars of planetary nebulae can proceed in several
distinct ways, either leading to H-deficiency or to H-normal surface
composition. Several new simulations of the evolution channels that lead to
H-deficiency are now available, mainly the born-again scenarios that are
triggered by a He-shell flash during the hot pre-white dwarf evolution phase. A
realistic AGB progenitor evolution is important for correct HRD tracks, that
allow mass determinations. New hydrodynamic simulations of He-shell flash
convection including cases with H-ingestion are now performed, and allow a
determination of the convective extra-mixing efficiency. This has direct
consequences for the intershell abundance distribution of AGB stars that can be
observed in the H-deficient CSPN.
