The carbon particle formation process in a pyrolysis of benzene and benzene-ethanol mixtures diluted by argon at initial temperatures 1650-2600 K and pressures 1.4-5.5 bar behind reflected shock waves was studied. The manifold optical diagnostics: emission-absorption spectroscopy for gas-particle temperature, time-resolved laser-induced incandescence (Ti-Re LII) for particle size evaluation and laser light extinction for the volume fraction of condensed phase measurements were applied simultaneously. The temperature in pyrolysis process was found to differ significantly from the initial temperature behind the reflected shock wave in all studied mixtures. The real temperature dependences of volume fraction of condensed phase at the wavelength of 633 nm and particle size based on the performed measurements were specified and analyzed. The effect of ethanol addition on carbon particle formation and reaction temperature in benzene pyrolysis is discussed. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.