The influences of hydrogen addition on laminar premixed ethanol/O-2/Ar and DME (dimethyl ether)/O-2/Ar flames under fuel-lean (Phi = 0.8) and fuel-rich (Phi = 1.7) conditions at 1.0 atm are studied by the detailed kinetic analysis. The comparisons are conducted to illustrate the characteristics of these two isomers affected by H2 addition. The chemical effects of H-2 addition on ethanol and dimethyl ether flames are distinguished and separated from its dilution and thermal effects respectively. The results show that the mole fractions of CH4, C2H6 and CH2O in DME flames are larger than those in ethanol flames. The influences of hydrogen addition on CH4, C2H6 and CH2O in ethanol flames are weakly. The chemical effects of H-2 addition promote the production of CH4, C2H6 and CH2O and shift the profiles to the upstream side in DME flames. The dilution and thermal effects which decrease the mole fractions of these species and shift profiles to the downstream side are more dominant for DME flames. Meanwhile, the mole fractions of C2H2, C2H4 and CH3CHO in DME flames are less than those in ethanol flames. The H-2 chemical effects which mainly promote the formation of C2H2 and C2H4 in ethanol flames suppress the production of these species in DME flames slightly for the fuel-rich condition. The dilution and thermal effects of hydrogen on these species are more dominant in ethanol flames than those in DME flames. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.