Detailed ab initio calculations on the lowest vibrational state of the electronic (C) over tilde T-2(2) manifold of CF4+ show a small Jahn-Teller effect in all asymmetric modes. This results in only small distortions from tetrahedral symmetry, but due to strong coupling between electronic and nuclear motions (dynamical Jahn-Teller effect), the spin-orbit splitting is reduced by an order of magnitude. This answers the outstanding question on the large differences between the results of electronic structure calculations and measurements on spin-orbit splittings in XY4 molecules or molecular ions [R. N. Dixon and R. P. Tuckett, Chem. Phys. Lett. 140, 553 (1987); J. F. M. Aarts and J. H. Callomon, Mol. Phys. 81, 1383 (1994)]. Complete agreement with experiment is however not reached because the dynamical Jahn-Teller effect is very sensitive to small errors in the potential energy surface. (C) 2000 American Institute of Physics. [S0021-9606(00)30309-9].