Quantum chemistry calculations at the B3LYP theory level, together with the 6-31G * basis set were employed to obtain energy (E), ionization potential (IP), bond dissociation energies (BDE), and spindensity distribution for aminophenol derivatives. Calculations of spin densities were performed for radical formed by hydrogen abstraction from the phenolic hydroxyl group. The IP and BDE values are related with more reactive and minus stable compounds. These values and also highest spin densities distribution on the phenolic oxygen shown that 4-regioisomer is more reactive and minus stable compounds, while 3-regioisomer is less reactive and more stable compounds.