The dehydrogenation of isobutane in the presence of CO₂ over NiO supported on γ-Al₂O₃ was investigated. For comparison, Cr₂O₃ supported on γ-Al₂O₃ was also investigated. Conventionally, catalysts used for the dehydrogenation of various alkanes suffer catalyst deactivation due to carbon deposition. In the present study, the yield of isobutene was significantly decreased with time-on-stream due to carbon deposition using Cr₂O₃(x)/γ-Al₂O₃, where x indicates the loading of a corresponding oxide by weight %. Carbon deposits were also evident on NiO(x)/γ-Al₂O₃; however, the yield of isobutene was enhanced with time-on-stream depending on the loading (x). This indicates that the contribution of the carbon deposition in the dehydrogenation on NiO(x)/γ-Al₂O₃ definitely differed from that on an ordinary catalyst system, such as Cr₂O₃(x)/γ-Al₂O₃. To confirm the advantageous effect of carbon deposition exerted on the yield of isobutene, NiO(x)/γ-Al₂O₃ was first treated with isobutane, following which its catalytic activity was examined. Predictably, it became clear that the carbon deposition during the pretreatment contributed to the enhancement of the isobutene yield. The presence of an Ni-carbide species together with the metallic Ni that was converted from NiO during the dehydrogenation definitely enhanced the yield of isobutene. Although carbon deposition is generally recognized as the main cause of catalyst deactivation, the results of the present study reveal that this is not necessarily the case.