In situ electrical conductivity measurements (ECMs) have been employed to gain insights into the redox and electronic behavior of ceria and surface-phosphated ceria catalysts with phosphorus contents lower than 2.2 at%. Temperature-programmed reduction under hydrogen (H2-TPR) was used to analyze the reducibility of the catalysts. Their propane oxydehydrogenation performance both in terms of activity and selectivity has been explained. It has been unambiguously shown that all the catalysts function via a heterogeneous redox mechanism involving only surface and subsurface lattice oxygen species whose availability and reactivity decrease with increasing phosphorus content with consequences on the catalytic performance.