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Photosynthetic pathways are reported for 305 species of Chenopodiaceae from Africa, Asia and Europe. Ecological characteristics, phytogeography and life forms of all species are given, and their correlation with relevant CO2-fixation types are discussed. 205 species (67.2%) exhibit the C-4-pathway and 100 species (32.8%) the C-3-pathway of CO2-fixation. Most of the C-4 species are of Irano-Turanian origin. The diversity of C-4 species of the Irano-Turanian phytochoria, with very harsh winters, are interpreted by the active period of Chenopods in summer. There is a close relationship between some special morphotypes and respective photosynthetic type. Halophytes and xerophytes with articulated stems and stem succulents of Anabasis-type are exclusively C-4 Leaf succulent halophytes and xerohalophytes are predominantly C-4. Hygrohalophytes with leaf or stem succulence are often C-3. Probably many C-4 Salsoleae have been evolved in the Afroasiatic arid zone after the climatic changes of the Miocene. Among them there is a high proportion of annuals that have a younger origin. There is some evidence that the present Chenopods of the subfamily ’’salsoboideae’’ may have their ancient stock in NW Africa, We found close taxonomic relationships between photosynthetic pathways and infrageneric classification in genera with both types of C-3 and C-4, like Atriplex and Suaeda.