2,3,6,7,10,11-Hexabromotriphenylene (HBTP) and 2,3,6,7,10-pentabromotriphenylene (PBTP) were investigated by means of dissociative electron attachment spectroscopy (DEAS). The dominant decay channel of the transient molecular negative ions consists of elimination of Br- with resonances in the low electron energy region. Formation of long-lived parent anions with autodetachment lifetime tau(a) = 310 mu s is observed at thermal electron energies. The adiabatic electron affinities, EA(a) = 1.12 +/- 0.1 eV in HBTP and 1.09 +/- 0.1 eV in PBTP, evaluated using a simple Arrhenius approach are in good agreement with those predicted by DFT (XYG3/Def2-TZVPP//PBEO/Def2-TZVPP) calculations.