The13C-NMR-spectrum of tropone is assigned precisely by the combined application of various methods (shift reagent technique, off-resonance at different decoupling frequencies for1H-13C shift correlation). The results confirm previously obtained data. The assignment of the thiotropone13C-NMR chemical shifts is brought about by a correlation between the respective thiotropone and tropone shift values at the same positions. This means that previously published data should be revised. The research deals with the shift effects (1.) during the change from carbonyl to the thiocarbonyl compound in the series tropone/thiotropone as well as the iso π electronic sulfur heterocycles thiopyrane-2-one/thiopyrane-2-thione 1,2-dithiole-3-one/1,2-dithiole-3-thione and 1,3-dithiole-2-one/1,3-dithiole-2-thione and (2.) in the series tropone, cyclohepta-2,4-dienone, cyclohepta-2,6-dienone, cyclohept-2-enone and cyclo-heptanone. In this series a transition from a shift sequence typical of α,β-unsaturated carbonyl compounds to a tropone like shift sequence can be observed.