The chemical effects of CO2 addition on premixed laminar low-pressure dimethyl ether and ethanol flames were studied by comprehensive numerical analysis from fuel-lean to fuel-rich conditions. Added CO2 is assumed as normal reactive CO2 and fictitious inert CO2 to assess the chemical effects of CO2. The dilution and thermal effects of CO2 addition decrease C2H2 mole fractions in ethanol flames instead of DME flames, but the chemical effects can reduce C2H2 mole fractions in both DME and ethanol flames at all equivalence ratios, which reveals that C2H2 formation can be suppressed chemically by CO2 addition. The chemical effects have a weak influence on formaldehyde formation in both DME and ethanol flames. The CO2 chemical effects only result in a slight decrease of acetaldehyde peak mole fractions in DME flames but not in ethanol flames at all equivalence ratios. Mole fractions of the H radical decrease because of the chemical effects of CO2 addition by shifting the equilibrium of CO + OH = CO2 + H in both DME and ethanol flames at all equivalence ratios, and mole fractions of OH and O radicals also decrease for equivalence ratios of 0.8, 1.0, and 1.2, whereas the chemical effects of added CO2 enhance the productions of OH and O radicals for rich conditions at an equivalence ratio of 1.5.