Results of long-term research of a hydrochemical regime of Kerzhenets river and its oxbows are presented. Oxbows are located at different distance from the river and have a different degree of fl owage and a subsoil waters, and also the different form of basin. It is recognized, that the hydrochemical conditions of oxbows depend mainly on a contribute of a subsoil waters, structure of thaved riwer waters and a superfi cial drain during rains. Freshet waters make a basis of water weight only of those lakes where the role of soil feed is insignifi cant. Seasonal fl ood water only temporarily equalizes limnological condition of oxbow lakes. After streams of water fall down, and lakes become disconnected from the river, qualitative structure of their waters and conditions of dwelling of hydrobionts become all more and more vairous because of local distinctions in morphology of hollows and features of a feed. Oxbows do not possess so stable conditions for hydrobionts what the river has. Distinctions with a river mode increase with distance from the river, increase of absolure height of oxbows concerning a river bed. Hydrobionts fi nd variety of conditions of existence in a fl ood-lands outside the basic river bed which become critical for their survival during the certain periods of year.