The structures of α-X-cyclopropyl and α-X-isopropyl radicals (X = H, O - , OH, NH 2 , CH 3 , NO 2 , CHO, CN, F and CF 3 ) are reported using MINDO-Forces MO method. In both radicals the planar structure is prefered over the pyramidal. All the substituents are stabilizing; the O - group is the most stabilizing substituent, while F group has little effect. O - , OH, F substituents are electron releasing groups on cyclopropyl ring, while NO 2 , CHO and CF 3 are electron widthdrawing. For isopropanes and x-X-isopropyl radicals, O - , OH, NH 2 and F act as electron releasing, while NO, and CF 3 act as electron withdrawing. The strain energies of the cyclopropyl radicals (43.8-23.7 kcal/mol) are compared with those of similarly substituted cyclopropanes. Dipole moments and spin densities are reported.