To measure the rate of spin-lattice relaxation in the Jahn-Teller active adamantane radical cation, the method of time-resolved magnetic effect in recombination fluorescence of spin-correlated radical ion pairs was applied. A very low value of about 6 +/- 1 ns was obtained for the relaxation time of the radical cation in magnetic field of 1 T. A rapid spin-lattice relaxation was also found in the cases of 1,3-dimethyladamantane and hexamethylenetetramine radical cations. Similarly to the case of benzene radical anion and cyclohexane radical cation, the relaxation is attributed to the spin-orbital interaction repeatedly arising in electronically degenerate states. (C) 2004 Elsevier B.V. All rights reserved.