Pb1-xMxWO4+delta (M = Pr, Tb) compounds with scheelite-type structure were synthesized and their conduction properties at higher temperatures were investigated. With the substitution of praseodymium or terbium ions, a large enhancement in conductivity of pure PbWO4 was observed and the transport number of oxide ions was found to be almost unity. Irrespective of the changeable valence of lanthanide ions substituted, conduction properties and defect structures of these systems were found to be similar to those of the other lanthanide (La or Sm)-substituted PbWO4.