A method based on 13C-NMR has been used as a tool for the identification and quantitative determination of two furanic sesquiterpenes: a heat-sensitive compound, furanodiene, and its rearrangement product, furanoelemene. Following a preliminary study using artificial mixtures which permitted the construction and verification of calibration curves for each compound, the method was used for the qualitative and quantitative analysis of furanodiene and furanoelemene in the essential oil of Smyrnium olusatrum.