A new coumarin, peuformosin (I), C₂₄H₂₆O₇, mp 155-156°, [α] ²⁷_D+67.3°, was isolated from ether extract of the root of Peucedanum formosanum HAYATA, in addition to (+)-anomalin, upon silica gel column chromatography, and was elucidated as 3'-angeloyloxy-4'-senecioyloxy-3', 4'-dihydroseselin from the fact that treatment of I with ethanolic sodium hydroxide under mild condition led to the formation of senecioic acid and 3'-angeloyloxy-4'-ethylkhellactone (VI) which yielded angelic acid and (+)-trans-ethylkhellactone (IIIc) upon further saponification. The ether extract of the root of Peucedanum japonicum THUNB. afforded a new coumarin, peucedanol (VII), C₁₄H₁₆O₅, mp 174-175°, [α]²⁰_D+31.2°, and a crystalline compound (XI), C₂₁H₂₂O₇, mp 90-96°. Peucedanol has three hydroxyl groups, one of which is phenolic. Oxidation of mono-O-methyl peucedanol (VIII) with sodium periodate yielded 6-formylmethyl-7-methoxycoumarin (X) with the formation of acetone, indicating that the structure of VII must be presented as 6-(2, 3-dihydroxy-3-methylbutyl)-7-hydroxycoumarin. The compound XI was presumed to be a mixture of acetyl-angeloylkhellactone (XIa) and acetyl- tigloylkhellactone (XIb) from NMR spectrum and the compsition of XI, and from the fact that treatment of XI with ethanolic sodium hydroxide yielded (±)-cis- (XIIb) and (±)-trans-ethylkhellactone (XIIa), and angelic, tiglic, and acetic acids.