To examine the taxonomic position and affinities of Isopyrum mandshuricum (Ranunculaceae) and related taxa, genetic analysis were carried out on the basis of isozyme patterns and ITS sequences. Molecular data, both isozyme patterns and ITS sequences suggest that I. mandshuricum is closely related to Enemion raddeanum than to Semiaquilegia adoxoides. The estimation of genetic identities by isozyme analysis reveals that I. manshuricum is genetically distant from E. raddeanum. The phylogenetic tree based on molecular data is rather congruent with the phenogram based on quantitative morphological characteristics, but not consistent with one based on qualitative morphological characteristics. Incongruencies between molecular and qualitative morphological data provide clues to re-evaluate several morphological features.