The equilibrium geometries, harmonic vibrational frequencies, and interaction energies of the Rg . NO+ (Rg = He, Ne, Ar, Kr, and Xe) cationic complexes are calculated using a variety of all-electron basis sets and effective core potentials augmented by polarization functions. Calculations are performed at the MP2, QCISD, QCISD(T), CCSD, and CCSD(T) levels of theory for Rg = He and Ne using the all-electron aug-cc-pVXZ [X = D, T, Q, and 5 (for He only)] basis sets; and at the MP2 and QCISD(T) levels for Rg = Ar, Kr, and Xe, using mainly effective core potentials, augmented with polarized valence basis sets. For Ar the results are compared with previous all-electron calculations, to confirm that the basis sets used are adequate. The results indicate that all the complexes are of a skewed T-shaped structure, with the Rg atom on the nitrogen side of the molecule; the Rg-N-O bond angle increases with mass. The interaction energies range from 195 cm(-1) for He . NO+ to 1980 cm(-1) for Xe . NO+, in line with expectations based on the increasing polarizability of the Rg atom.