For two representative delocalized PAH-carbocations, namely the C-1 protonated 4H-cyclopenta[def]phenanthrenium cation 1H⁺ and the C-1 protonated pyrenium cation 2H⁺, generated in FSO₃H–SO₂ClF, the FSO₃H∶PAH molar ratio and the absolute concentration of the arenium ions were systematically varied over a wide range (FSO₃H∶PAH molar ratios were varied from 71 to 1 for 1H⁺ and from 69 to 5 for 2H⁺ in 0.3 mL of SO₂ClF and 0.05 mL of CD₂Cl₂ at –75 °C). In selected cases, the H/H COSY and C/H HETCOR spectra were used to fully assign the resonances. Shielding of the PAH-arenium ion protons and carbons was observed with decreasing FSO₃H∶PAH ratios without noticeable line-broadening. This is attributed to cation–anion interactions in the low FSO₃H∶PAH domain and possible formation of contact ion pairs. Lowering the ratio (below 35 in the case of 1 and below 10 for 2) gave separate sets of resonances for the unprotonated PAH, indicative of the presence of the equilibrium: PAH + FSO₃H⇌PAHH⁺ + FSO₃^–. The observed shielding of the unprotonated PAH in the equilibrium as compared to the starting material in CDCl₃, is attributed to solvation by FSO₃H, although possible formation of PAHH⁺ FSO₃^––PAH ion pair–molecule clusters is not ruled out.