We have investigated the phase changes in CdTiO3 nanofibers as the annealing temperature of nanofibers was increased from 600 to 1200 degrees C. The nanofibers annealed at 600 degrees C were ilmenite with a very small amount of CdO. Upon annealing at 950 degrees C, CdO was completely removed. Annealing at 1000 degrees C yielded pure perovskite nanofibers, and at temperatures above 1100 degrees C rutile TiO2 nanofibers were obtained. Brunauer-Emmett-Teller (BET) analysis showed that with increase in annealing temperature the surface area of nanofibers was decreased. The nanofibers annealed at 600 degrees C have the higher surface area of similar to 9.41 m(2)/g. Then oxygen sensors using CdTiO3 nanofibers annealed at 600 degrees C (ilmenite) and 1000 degrees C (perovskite) were fabricated. The sensitivity of the ilmenite nanofibers sensor was 2 times than that of the perovskite nanofibers sensor. The response and recovery times were 120 and 23 s, respectively, for the ilmenite nanofibers sensor, whereas response and recovery times were 156 and 50 s, respectively, for the perovskite nanofibers sensor. Better oxygen characteristics of ilmenite nanofibers are attributed to their large surface area and porosity. Therefore, we believe that ilmenite CdTiO3 nanofibers are potential candidates to develop practical oxygen sensors.