A thermochemical study of the p-benzoquinone and the duroquinone has been performed by different calorimetric techniques. Applying heat flux calorimetry and differential scanning calorimetry, the enthalpies of fusion for each substance were measured. Enthalpies of combustion in condensed phase were determined by static bomb combustion calorimetry hence the enthalpies of formation in solid phase were derived. Data of enthalpy of sublimation of both compounds were obtained by d.s.c. and independently by using a quartz crystal microbalance, and then applied to derive the enthalpy of formation in gas phase of these benzoquinones. From this set of experimental data, resonance, isodesmic, and homodesmotic stabilization energies were computed. Results made it possible to elucidate that the p-benzoquinone is antiaromatic while the duroquinone is an aromatic compound. (C) 2004 Elsevier Ltd. All rights reserved.