The dissociative photodetachment (DPD) of HCO2- and DCO2- was studied at 258 nm. State-resolved translational energy distributions were observed correlated to bending excitation in the CO2 product for the channel producing H/D+CO2, indicating very low rotational excitation in the products consistent with predissociation of a C-2v HCO2 molecule. No evidence was found for dissociation into OH+CO. All three low-lying electronic states ((2)A(1), B-2(2), and (2)A(2)) were found to dissociate, but resolved progressions were only observed from photodetachment to the (2)A(1) and B-2(2) states. Photoelectron-photofragment coincidence spectra for DCO2- show resolved vertical bands and indicate that multiple CO2 vibrational states are accessible from each vibrational level in the predissociating DCO2 molecule. The resolved structure is assigned to vibrational predissociation sequence bands, observable in this DPD process owing to the dissociation dynamics and the near degeneracy of the vibrational levels in the (2)A(1) and B-2(2) states of HCO2 and the bending mode of the CO2 products.