Based on extensive ab initio calculations of the hyperfine coupling constants of both hydrogen and carbon nuclei of three C2H2- anions, it is confirmed that an acetylene radical anion has effectively been produced radiolytically in low temperature alkane matrices and it possesses a trans-bent form. The results are derived from different molecular orbital configuration interaction calculations (CIS, CISD, QCISD and MRD-CI) as well as density functional theory (DFT) employing extended basis sets. Both popular DFT methods (BLYP and B3LYP) show some difficulties in calculating the isotropic coupling constants of the carbon nuclei.