A solid phase extraction-flow injection procedure for online determination of Cu(II) by flame atomic absorption spectrometry (FI-AAS) has been reported. The metal ions are retained as Cu(I)-neocuproine complex in a mini-column filled with octadecyl bonded silica (C-18) as sorbent material. Quantitative extraction has been obtained at pH 5.0. The retained metal ions are then eluted efficiently with ethanol into the nebulizer of flame atomic absorption spectrometer for on-line determination. Different variables affecting the preconcentration efficiency, including pH, neocuproine concentration, eluent type, sample, eluent flow rates and sample loading time, are optimized. Two minute preconcentration at flow rate of 6 mL min(-1) provides the enhancement factor of 100 for Cu(II). The detection limit (3 sigma) is found to be 0.15 mu g L-1 for Cu(II), and the relative standard deviation at 5.0 mu g L-1 of target metal ions is 1.2% (n=7). The accuracy has been assessed by analysis of certified reference materials CASS-4 and CRM1643d, and the obtained results are found in good agreement with certified amounts of Cu(II). The procedure has been applied successfully to Cu(II) ion determination in water samples.