Adiabatic electron affinities, optimized molecular geometries, and 1R-active vibrational frequencies have been predicted for small cyclic hydrocarbon radicals CnH2n-1 (n = 3-6) and their perfluoro counterparts CnF2n-1 (n = 3-6). Total energies and optimized geometries of the radicals and corresponding anions have been obtained using carefully calibrated (Chem. Rev. 2002, 102, 231) density functional methods, namely, the B3LYP, BLYP, and BP86 functionals in conjunction with the DZP++ basis set. The predicted electron affinities show that only the cyclopropyl radical tends to bind electrons among the hydrocarbon radicals studied. The trend for the perfluorocarbon (PFC) radicals is quite different. The electron affinities increase with expanding ring size until n = 5 and then slightly decrease at n = 6. Predicted electron affinities of the hydrocarbon radicals using the B3LYP hybrid functional are 0.24 eV (C3H5/C3H5-), -0.19 eV (C4H7/C4H7-), -0.15 eV (C5H9/C5H9-), and -0.11 eV (C6H11/C6H11-). Analogous electron affinities of the perflurocarbon radicals are 2.81 eV (C3F5/C3F5-), 3.18 eV (C4F7/C4F7-), 3.34 eV (C5F9/C5F9-), and 3.21 eV (C6F11/C6F11-).