In this study three major types of preconcentration methods based upon different principles (cation exchange, physical absorption and hydrophobic extraction) were evaluated and optimized for the extraction and determination of three highly toxic heavy metals namely Cd, Ph and Sn by graphite furnace and hybrid generation atomic absorption spectrometry in real samples. The optimum analytical condition were examined and the analytical features of each method were revealed and compared. Detection limit: as low as 0.003-0.025 mu g L-1 for Cd2+, 0.05-0.10 mu g L-1 for Pb2+ and 0.1-0.25 mu g L-1 for Sn4+ depending on the extraction method were obtained with RSD values between 3.08% and 6.11%. A preliminary assessment of the pollution status of three important natural ecosystems in Epirus region (NW Greece) was performed and some early conclusions were drawn and discussed. (C) 2008 Published by Elsevier B.V.