Effect of ethanol (EtOH) addition to unburnt gas mixture on the species pool in a fuel-rich flat, premixed, laminar ethylene flame at atmospheric pressure is studied experimentally and by chemical kinetic modeling. Mole fraction profiles as a function of height above burner of various stable and labile species including reactants, major products and intermediates (C-1-C-4 hydrocarbons) are measured using molecular beam mass spectrometry with electron ionization in C2H4/O-2/Ar and C2H4/EtOH/O-2/Ar flames. The experimental profiles are compared with those calculated using three different chemical kinetic mechanisms. Performances and deficiencies of the mechanisms are discussed. An analysis of the mechanisms is carried out in order to identify the reason of the ethanol effect on the mole fraction of propargyl, the main precursor of benzene. A modification of some mechanisms in order to improve their capability to predict acetylene and diacetylene mole fraction profiles is proposed. (C) 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.