For the synthesis of the coumarin based column packing materials, amino functionalized porous silica was prepared from the modification of silica with 3-aminopropyl triethoxysilane. This amino functional silica was reacted with 4-chloromethyl-7,8-dihydroxycoumarin. The produced silica based column packing material was characterized by spectral techniques, scanning electron microscope, X-ray diffraction analysis (X-ray), N-2 adsorption isotherms and thermal analysis techniques. The effect of coumarin group on the silica structure and separation properties as well as the thermal stability of materials was investigated. Average particle diameters, pore size and surface areas of the coumarin based silica particles were 2680 +/- A 750 mu m, similar to 33 nm and 118 +/- A 6 m(2)/g, respectively. 240 mm x 4.6 mm high performance liquid chromatography column was packed with coumarin functionalized porous silica. Then, this column was applied to the separation of similar structure aromatic compounds such as benzene, toluene and xylene. Column performance was investigated by measuring time of continuous use peak asymmetry, resolution, and selectivity. Chromatographic resolutions of coumarin-modified packing material were in the range of 2.28-2.35. According to these data, for the separation of aromatic compounds, while pure silica does not provide effective separation, coumarin based column packing material has showed good separation and selectivity.