Two new triatomic molecular ions with C2v symmetry i.e. CO2– and SO2– have been detected in NaCl by means of EPR. By analysing the 13C hyperfine tensor of the CO2– radical the spin densities in the 2s and 2pz carbon atomic orbitals can be calculated. Since the 14N hyperfine tensor of the isoelectronic NO2 molecule in the same host lattice is also known, a comparison between the spin densities in both defects can be made. In addition, the spin densities for both defects are calculated using ab initio methods and are compared with the experimental results.As is the case for the smaller CO2– ion, the SO2– radical is assumed to substitute for only one halide ion. The monovacancy model for the SO2– ion is discussed. Such a model is in accordance with that for the smaller ozonide O3– ion. On the other hand, the larger S3 and Se3– ions occupy a trivacancy site.