Two different types of radical cations have been studied by means of density functional theory (BLYP) and mixed Hartree-Fock/DFT (B3LYP) calculations. For the description of the structure and the vibrational frequencies of aromatic amine radical cations the latter is the best practical method, as illustrated for the case of N,N,N’,N’-tetramethyl-p-phenylenediamine. For the through-bond coupled radical cations of piperazine derivatives, HF calculations give completely incorrect results due to the tendency to localize the positive charge on one of the amino groups. Post-I-IF corrections are troublesome. The DFT calculations do not suffer from this problem, which gives them a unique advantage over HF methods in this case.