Substituent chemical shifts (measured at natural abundance at 0 . 4 ~ concentration) and calculated (ab initio, STO-3G) electron densities at the nitrogen and oxygen (or sulphur) are reported for series of paraand rneta-substituted benzamides and thiobenzamides with NMe,, NH,, OMe, NJ3COMe, F, C1, Br, I, Me, H, COMe, COOMe, CF,, CN, NO,, CONH, and CSNJ3, substituents. The '"N shifts are very sensitive to the substituent effects. The dual substituent parameter method shows excellent correlations of '"N shifts against substituent field and resonance effects, with the sensitivity in the thiobenzamides being double that in the benzamides. In contrast, calculated n-electron densities at the nitrogen show the same sensitivity to substituents in both series. The '"N shifts correlate well with the calculated n-electron densities at the nitrogen; however, estimates of the shielding based on local electron densities (described in Pople's independent electron model) cannot aeconnt for the increased sensitivity to the substituent effects observed for 'SN chemical shifts of thiobenzamides. It is suggested that non-local shielding from sulphur and oxygen are responsible for the chemical shift trends.