The crystal structure of the cumyl cation (1; 2-phenyl-2-propyl cation) has been determined at -124 degrees C (as hexafluoroantimonate, 1 . SbF6; R(1) = 0.0502, wR(2) = 0.1054). The cation 1 is nearly planar and has a short C+-C-ipso bond (1.41(2) Angstrom) and bond lengths in the phenyl ring which agree with strong benzylic delocalization. The weak but distinct shortening of the C+-CH3 bonds by 0.025(12) Angstrom indicates weak C-H hyperconjugation. Nearly all H atoms are involved in H ... F contacts to SbF6 anions, and one close C+... F contact (3.11(2) Angstrom) is observed. The phenyl rings form infinite stacks and are shifted against each other in the stack.