Electrical properties of Gd2(WO4)3 and Ho2(WO4)3 were studied and the type of charge carriers was determined. The studied compounds have a salt-like isle structure with isolated tetrahedrons. It crystallises in the Еu2(WO4)3 structural type, so-called ‘defective scheelite’, in which 1/3 of Ln sites are vacant, Ln2/3[VLn]1/3WO4. Predominant ionic conductivity in Ln2(WO4)3 (Ln = Gd, Ho) was established both by the EMF method and from independence of conductivity versus oxygen partial pressure. A minor contribution (4-11%) of the anion [WO4]2- transport was detected by the Tubandt method, which along with the results of the EMF technique proves the predominant oxygen conductivity.