The predominant tautomeric forms of N1-H, N2-H of 5-(2,6-dimethyl-and 5-(2,6-diisopropylphenoxy)-(1H)-tetrazoles were analyzed at B3LYP method using 6-311G(d,p) basis set in the gas phase. The N1-H form of tetrazoles was found to be more stable than N2-H form in both solid and gas phases. Crystal structures of both tetrazoles show an intermolecular Hbond between N1-H and N4 atom of other tetrazole space. The hydrogen bonds between each tautomer of tetrazoles were evaluated at B3LYP/6-311G(d,p) level. The geometrical parameters and spectral data of tetrazoles and their variation were studied in both solid and gas phases.