Thin films of cobalt oxide have been prepared by reactive sputtering and the spinel CoCo 2 O 4 structure together with p-type sensing behavior has been achieved. Structural and morphological studies have been carried out by means of SEM, TEM and XRI in order to investigate the correlation between the deposition parameter and the sensing performance. The films proved to be sensitive to ethanol, carbon oxide, benzene and nitrogen dioxide. It was also shown that annealing temperature influences the grain size of the nanosized cobalt oxide grains