Theoretical calculations focused on the ability of an AlN nanosheet to detect O(3) and SO(2) molecules based on the dispersion corrected B3LYP (B3LYP-D) and B97D density functionals. Equilibrium geometries, stabilities, and the electronic properties of O(3) and SO(2) adsorptions on the surface of an AlN sheet were explored. The adsorption energies were calculated to be about -17.80 and -21.51 kcal mol(-1) at B3LYP-D level for O(3) and SO(2) corresponding to the most stable configurations, respectively. It was shown that the electrical conductance of the AlN sheet may be increased after the SO(2) adsorption, being somewhat insensitive to the O(3) adsorption. Thus, the AlN sheet may selectively detect SO(2) molecules in the presence of O(3) molecules.