A comparative investigation of gaseous products formed by gamma-irradiation of poly(1,4-butylene terephthalate), PBT; poly(ethylene terephthalate), PET; and poly(ethylene 2,6-naphthalene-dicarboxylate), PEN has been performed. These polyesters were irradiated under vacuum at doses from 0.5 to 4 MGy. The gases formed were analyzed by gas chromatography -mass spectrometry, and their radiation-chemical yields (G) were calculated. Hydrogen, carbon monoxide and carbon dioxide, as the main products, and methane of low quantity were found after radiolysis of all polyesters studied. Other hydrocarbons such as ethane, propane, propene and n-butane were also detected in gases mixture resulted from irradiation of PBT. Traces of ethane were also registered in the radiolysis products of PET. Irradiation of PEN did not lead to formation of hydrocarbons other than methane. The total G values and compositions of the formed gaseous mixtures depended on chemical structure of the irradiated polyesters. Mechanism of gaseous products formation has been discussed.