The Raman spectra of the phenyl esters of cinnamic and benozic acids have been studied and those of the methyl and ethyl esters of the above acids along with that of phenyl acetate have been reinvestigated. From the above data and those obtained by other workers relating to alkyl and phenyl esters and some other carbonyl compounds the C=O frequencies have been tabulated. It is noted that the phenyl group attached directly to the carbon of the C=O group as in esters of aromatic acids and in aromatic ketones, etc., markedly lowers the carbonyl frequency whereas the same group attached to the oxygen atom of the COO group definitely enhances the frequency. These facts are explained from considerations of electromeric polarisation and resonance.