The neoclassical transport theory of a toroidal plasma in the presence of ion impurities is investigated. In particular, referring to situations with hydrogen ions and electrons in the banana regime, the two possibilities, of the impurity ions being in the banana or in the plateau regime, are considered. It is found that, in the small aspect ratio limit and for practical values of impurity concentrations, the hydrogen ion diffusion across the magnetic field does not depend on the neoclassical regime of the impurities.