The fragmentation pathways of 2-hydroxyphenol and 2,3-di-hydroxyphenol have been examined using electron impact mass spectrometry in comparison with thermal analyses (TGA and DTA). Both the decomposition modes were investigated, and the fragmentation pathways were suggested. The combined use of mass spectrometry and thermogravimetry (MS and TG) in the analysis of 2-hydroxyphenol and 2,3-di-hydroxyphenol allowed the characterization of the fragmentation pathway in MS which was the objective of this research. The major pathway of hydroxyphenol includes successive loss of CHO. while 2,3-di-hydroxyphenol the major pathway involved loss of H2O followed by CO. There was virtually no ring disintegration until the majority of the attached groups were lost in 2-hydroxyphenol. while in 2,3-di-hydroxyphenol a complete decomposition occurred. On the other hand. an O atom remains attached to five-membered ring in a cyclopentanone form as a result of the stability of PG in comparison with PC. The thermal decomposition and mass spectral fragmentation of the hydroxybenzene are also correlated with the electron delocalization of their ring system.