13C-n.m.r. chemical shifts of 10 acrylophenones (1-substituted phenylprop-2-en-1-ones) are reported. The additivity parameters for the substituent effect of the acryloyl group in the aromatic ring and of the benzoyl group in ethylene were calculated. Comparison of ethene chemical shifts in chalcones (1,3-diphenylpropenones) with calculated values yielded good results, showing that cross conjugation in these molecules is of little importance. Chemical shifts in acrylophenones and chalcones can therefore be calculated as linear combinations of the mutual effects of the constituent groups.