A simple and sensitive on-line preconcentration procedure was developed for the determination of trace levels of cadmium(II) by flame atomic absorption spectrometry. A mini-column packed with a chloromethylated polystyrene functionalized with N,N-bis(naphthylideneimino)diethylenetriamine (NAPdein) was used for the on-line enrichment of cadmium(II) at pH 7.0. All chemical and flow injection variables were optimized for the quantitative preconcentration and determination of cadmium(II). Under the optimum conditions, the calibration graph obtained was linear over the concentration rang of 1.00-30.0 microg L(-1). The detection limit (DL) and enrichment factor were 0.25 microg L(-1) and 50-fold, respectively. The relative standard deviations for 7 replicate determinations of cadmium(II) at the 2.0 and 20 microg L(-1) levels were 5.1% and 2.2%, respectively. The effect of the presence of various species commonly associated with real samples was also investigated. The accuracy of the proposed method was demonstrated by analyzing different water samples.