The study of a set of 3-benzylidene-4-chromanones, 3-bemyl-4-rhromanones, 3-bemyl-3-hydroxy-4-chromanones and 3-benzylchromones (homoisollavonoids) by 13C NMR spect~oscopy shows the influence of the structure of these molecules on the chemical shifts of the more characteristic carbon atoms at positions 2, 3 and 4.