The organic matter content in original and chemically treated olive oil mill wastewater obtained from a three phase extraction plant was profiled by a resin fractionation procedure to evaluate changes in its characteristics after acid cracking as well as chemical treatment by FeCl3 coagulation, electrocoagulation with stainless steel electrodes, and an advanced oxidation processes (Fenton's reagent). For this purpose, untreated, acid-cracked, and chemically treated wastewater samples were fractionated into hydrophobic and hydrophilic (acid-base-neutral) structures using XAD-8, XAD-4, AG-MP-50, and Duolite A-7 resins. Structural distribution analysis of the untreated samples indicated that hydrophobic structures were the major (75-95%) components of the wastewater's organic matter content. For the total phenols parameter, a significant fraction (56%) appeared to be hydrophobic neutral coinciding with the acute toxicity of the olive oil mill wastewater. A significant amount of oil and grease as well as particulate organic matter could be removed by subjecting the original wastewater sample to acid cracking. FeCl3 coagulation appeared to be effective in the removal of hydrophobic fractions whereas electrocoagulation and the Fenton's reagent were also effective in the removal of hydrophilic organic matter. After chemical treatment of the olive oil mill wastewater, a significant shift in its structural distribution pattern was observed from mainly hydrophobic to more hydrophilic fractions.