An experimental study of OH*, CHO*, CH* and C-2* radicals in excited electronic states present in C2H2/O-2 and C2H2/O-2/Ar flames was carry out. Measurements of natural emissions of these species as a function of time were obtained for several combustion processes in a closed chamber. The emission times of all radicals for both C2H2/O-2 and C2H2/O-2/Ar flames were found to decrease with the increase of Phi from 0.30 to 0.68 and were almost the same Phi = 0.68, Phi = 1.00 and Phi = 1.62. CH*, The C-2* production efficiencies were almost constant in the range to Phi > 0.30, while the production efficiencies of OH* and CHO* radicals were reduced as Phi increased. The addition of argon to increase the total initial pressure had practically no effect on the chemiluminescence of radicals, except for the fuel-lean combustion (Phi = 0.30), in which the production efficiencies of excited radicals was reduced.