Six new layered lanthanide molybdate and tungstate phases pillared by either naphthalenedisulfonate (NDS) or fumarate anions have been synthesized hydrothermally and structurally characterized. Five of these materials, [Nd(H2O)MoO4](2)[2,6-NDS] (1), [Nd(H2O)MoO4](2)[1,5-NDS] (2), [La(H2O)WO4](2)[1,5-NDS] (3), [La(H2O)WO4](2)[2,6-NDS] (4), and [Ce(H2O)MoO4](2)[fumarate] (6), have a closely related cationic inorganic layer structure which comprises a bilayer of polyhedra leading to the formation of a framework layer containing small, inaccessible pores. These layers are pillared by the organic anions which also bridge between the lanthanide cations within the layers. In the La/WO4/2,6-NDS system, a second polymorph, [La-2(H2O)(2)W2O8][2,6-NDS] (5), is observed. In this compound, the tungstate anions have dimerized, forming W2O84-. This dimer is unique and comprises two square-based pyramidal tungsten centers which are opposed to each other.