A fast method for separation, preconcentration and determination of cadmium in drinking (source, well, tap) and water for irrigation is described. Iron(III) hexamethylenedithiocarbamate, Fe(HMDTC)3, has the role of colloid precipitate flotation collector. The determination of cadmium in final water solutions preconcentrated by flotation can be performed by flame (FAAS) or electrothermal atomic absorption spectrometry (ETAAS). The method applied, either FAAS or ETAAS, depends of the concentration level of analyte in the water sample investigating. The AAS results are compared with inductively coupled plasma-atomic emission spectrometric measurements (ICP-AES) as an independent method. The ETAAS detection limit of cadmium is 0.002 microgram/L.