The paper presents results of a study on the population structure of the orchid Liparis loeselii growing in the Warta River valley peat bog in Myszków (Woźnicko-Wieluńska Upland, S. Poland). Individuals of L. loeselii occurred in patches of Menyantho trifoliatae-Sphagnetum teretis and Eleocharitetum pauciflorae – associations. The demographic structure of L. loeselii populations was described by variations in plant height, the length and width of leaves and the number of flowers of the constituting individuals. It was observed that habitat conditions such as conductivity, pH and the percentage cover of tall perennials had the strongest effect on the structure of L. loeselii populations.