The fine structure of the copper L3 edge in fcc Cu was simulated using a full potential linearised augmented plane wave method (WIEN97). The computations were based on a single cell-model by introducing a partial core hole and on a 2 x 2 x 1 super-cell-model with one full core hole. No difference between the single cell with a full core hole and the 16 atoms supercell with one core hole could be observed. Comparison with experimental spectra of two Cu specimens prepared by different methods showed that after removing the Cu2O contribution to the spectrum the best fit was obtained for half a core hole. This shows that the core hole in Cu metal is only partially screened by the valence electrons.