Lycopodiella inundata is an endangered, wetland species, able to occur in secondary, anthropogenic habitats. The article presents five-year changes in the occurrence of Lycopodiella inundata on the one of the largest stands in Central Poland. Chosen parameters of population were examined in different stages of vegetation succession. In open thickets the number of fertile stems was near three times higher and amounted above eight hundred fertile stems per square meter. In contrast, in patches with dense herb- and shrub-layer, the low number of fertile stems of L. inundata, have been observed. At anthropogenic sites, where L. inundata occurs, active protection should be made for the inhibition of succession and for the rejuvenation of habitat.