AbstractThe acidic components from the wood of Libocedrus formosana, Florin were studied. Thujic acid (4,4‐dimethyl‐2,5,7‐cycloheptatriene carbo‐xylic acid) and shonanic acid were isolated. The structure of shonanic acid would be 4, 4‐di‐methyl‐?, ?‐cycloheptadiene carboxylic acid rather than Ichikawa's 5, 5‐dimethyl, 4‐methylene‐2‐cyclohexene carboxylic acid as revealed by the data of its infrared and ultra‐violet absorption spectra and the results o