In this project of the PUTTE-program (poorly known habitats and species) of Ministry of Environment we study vegetation types and species of rich fens (’letto’ in Finnish). These habitats are among the most threatened and have special biodiversity values. We collect all possible vegetation plot data that exists from Finnish rich fens and amend it in a field work campaign. The data base will enable revision of vegetation classification of rich fens and presentation of their distribution. We also produce information of rich-fen species occurrences with specific focus on poorly known molluscs and hepatics.