In this work it was studied the influence of cross-interference effects between hydrogen and ozone on the performances of the SnO2-based thin film gas sensors. The SnO2 films with different thickness were deposited by spray pyrolysis. It was shown that the interference of gases was not a simple arithmetic addition of two effects related to the influence of individual gases on the sensor parameters. Interference of gases depends on many factors, including the concentration of the interacting gases, the film structure and the surface properties of the gas-sensitive material. Therefore it is difficult to predict this effect basing on the results obtained during the sensor testing to individual gases. It was also found that the air ozonization could be used to optimize the sensor parameters, i.e. to increase sensitivity and decrease the time constants of response and recovery. In addition, we have proposed temperature conditions, providing an improvement of the sensor selectivity when detecting hydrogen and ozone.