A printing medium comprising a substrate having at least one surface and a coating on the surface wherein the coating comprises: (a) binder comprising: (1) organic polymer which is substantially free of onium groups, and (2) onium addition polymer consisting essentially of onium-containing mer units derived from addition monomer and onium-free mer units derived from addition monomer of which from 20 to 100 percent by weight is hydrophobic addition monomer, wherein the binder constitutes from 20 to 90 percent by weight of the coating; and (b) finely divided substantially water-insoluble pseudoboehmite particles which have a maximum dimension of less than 500 nanometers, are distributed throughout the binder, and constitute from 10 to 80 percent by weight of the coating.