Comparative anatomy of six taxa of Cyperus distributed in the north of Iran was studied. The investigated species are: C. difformis, C. distachyos, C. fuscus, C. pygmaeus, C. odoratus subsp. transcaucasicus, and C. rotundus. Cross sections of stems and leaves of these species were examined. The following characters were determined to be taxonomically informative: cross-section shape of the aerial stem, presence or absence of vascular bundle in the central part of stem cross-sections, the diameter of mesophyll and air cavities in stem and leaf cross-sections. Cyperus fuscus and C. difformis differ from other studied species in having large air cavities in stem and leaf cross section. Our results show that comparative anatomy of lateral stems and leaves may provide additional characters to be considered in taxonomic studies within this genus.