CaO-NiO/Al2O3 catalysts were prepared by wet impregnation method, keeping the NiO composition constant at 25 wt.% and varying the CaO composition in the range 6-12 wt.%. The catalysts were evaluated for oxidative dehydrogenation (ODH) of ethane with CO2 at atmospheric pressure and in the temperature range of 600-700 A degrees C. The physicochemical characterization of the catalysts was carried out using X-ray diffraction (XRD), BET surface area, Temperature programmed reduction (TPR), Temperature programmed desorption of CO2 (CO2-TPD), H-2 chemisorption, Carbon analysis and Fourier transform infrared (FT-IR) spectroscopy. NiO/Al2O3 showed higher ethane and carbon dioxide conversions, but with lower ethene selectivity. The addition of CaO in NiO/Al2O3 reversed the course of reaction leading to high selectivity to ethene, although at reduced conversions. 9 wt.% CaO containing NiO/Al2O3 emerged as the most promising catalyst giving the highest yield of ethene. CaO addition increased the basicity and the coke resistance. The shift in selectivity with CaO addition is explained in terms of more probability for reverse water gas shift reaction on a basic site rather than the hydrocracking reaction on the acidic sites of Ni/Al2O3. The 9 wt.% CaO-25% NiO/Al2O3 catalysts were also prepared by changing the sequence of impregnation and by adopting simultaneous deposition of the two oxides on Al2O3. The activity of these catalysts was compared to identify the best method of catalyst preparation. Ca promotion of NiAl modifies the surface basic property increasing ethene/methane selectivity ratio from 1 to 4, and enhances coke resistance. [GRAPHICS]