Gamma radiation-induced radicals in poly(β-alanine), poly(α-methyl-β-alanine) and poly(β-methyl-β-alanine) have been investigated by Electron Spin Resonance Spectrometry technique. ESR spectra of polymers irradiated in nitrogen and air have been simulated by curve fitting software (Winsim2002). The type of radicals generated, their relative abundances, conversion into other radicalic species and their room temperature stability were evaluated. At least two types of radicals have been detected for each polymer. Most stable radicals have been obtained in the case of poly(α-methyl-β-alanine).