The hydride transfer and proton transfer occurring between the constituents of ion/neutral complexes of tert-butyl cations and electron-rich and electron-poor 1,3-diphenylpropanes, [(CH 3 ) 3 C + C 6 H 5 CH 2 CH 2 CH 2 C 6 H 4 X] were investigated by use of CI/MIKE spectrometry of nine 1-(tert-butylphenyl)-3-arylpropanes and 16 site-specific deuterium-labeled isotopomers. The competition between H − abstraction by the (CH 3 ) 3 C + ion from the neutral arene and H + transfer to it was found to be strongly affected by the electron-donating substituents, in particular by X=OCH 3 , on the one hand, and X=F and CF 3 , on the other, suggesting that the 1,3-diphenylpropane molecule within the I/N complex acts and reacts as a bidentate solvating partner to the carbocation. The effect of the substituents X on the regioselectivity of the intra-complex hydride abstraction from the two benzylic CH 2 groups, k γ-H /k α-H , and their influence on the kinetic isotope effect (k H /k D ) γ , operating during the abstraction from the substituted benzylic moiety, were determined in a semi-quantitative approach by assuming (k H /k D ) α =1.60, the generally observed value for the unsubstituted benzylic moiety. The regioselectivity range was found to span almost three orders of magnitude, from k γ-H /k α-H ≥11.2 for the complex [(CH 3 ) 3 C + C 6 H 5 C α H 2 CH 2 C γ H 2 C 6 H 4 (p-OCH 3 )] to k γ-H /k α-H ≤0.04 for the complex [(CH 3 ) 3 C + C 6 H 5 C α H 2 CH 2 C γ H 2 C 6 H 4 (p-CF 3 )].