Recently, cyclodextrin derivatives were reported to increase significantly the half-life of the spin adducts resulting from the trapping of free radicals with nitrones. To address the physicochemical characteristics of these complexes, a series of alpha-phenyl-N-tert-butylnitrone (PBN) analogues containing hydroxy groups on the tert-butyl group was prepared. The influence of the substitution on the supramolecular complexation of the nitrones with natural beta-cyclodextrin was studied by NMR spectroscopy. 1D-NMR studies indicated a 1: 1 stoichiometry and binding constants in the range 32 to 1075 M-1 depending on the substitution pattern. 2D-NMR experiments suggested a competitive inclusion of the PBN derivatives by the aryl moiety through the two accessible wide and narrow rims of the cyclodextrin.