Complex oxides within the family CeNbO4 have been shown by single crystal x-ray studies to have superstructured average structures, but little detail has been obtained about the nature of the oxygen positions in these materials. The crystallographic structure gives little hint on the realtionship between the structure of the related phases CeNbO4, CeNbO4.08 and CeNbO4.25 and of the fast ion conduction present at low temperatures in the CeNbO4.25 composition. It is assumed that the conduction mechanism in this composition must be related to variations in the local structure that are not apparent from the average structure. It is therefore the intention of this work to use a PDF approach to investigate each composition and to extract details of the conduction mechanism from these measurements. We will therefore determined the local structure of each composition as a function of T.