The compounds containing either 1,3-diphenyl-1,2,3,4-tetrazolium or 2,3-diphenyl-1,2,3,4-tetrazolium ring have been investigated by means of 14N and 15N NMR technique. The effects of structure variation on the change in N chemical shifts are dis-cussed. Positive charge distribution within tetrazolium ring has been examined by N NMR technique.