In this work, we have determined the experimental standard (p° = 0.1 MPa) molar enthalpies of formation, in gas phase, of flavone and flavanone. These results were obtained by combining the standard molar enthalpies of formation in the condensed phase with the standard molar enthalpies of sublimation. The former values were derived from combustion experiments in oxygen, at T = 298.15 K, in a static bomb calorimeter. The values of the standard molar enthalpies of sublimation were obtained by Calvet microcalorimetry and corrected to T = 298.15 K. High-level density functional theory calculations using the B3LYP hybrid exchange-correlation energy functional with extended basis sets and more accurate correlated computational techniques of the MCCM/3 suite have been performed for the compounds. The obtained results, experimental and computational, for flavone and flavanone were compared with those obtained for chromone and chromanone, respectively.