The gas-phase Proton Affinity (PA) and Basicity (GB) of 2-, 3- and 4-hydroxybenzophenone isomers have been experimentally determined by the Extended Kinetic Cooks Method (EKCM), using ESI-TQ Mass Spectrometry. Our results show that 4-hydroxybenzophenone isomer (PA = 912.6 +/- 8.4 kJ.mol(-1)) is in the order of 10 kJ.mol(-1) more basic than the 2- and 3-hydroxybenzophenones isomers. The results have been rationalized and discussed by means of computational DFT calculations at B3LYP/6-311 + + G(d,p) level of theory.