A study was carried out on the occurrence of chitinolytic bacteria inhabiting surface water, water above the sediment and bottom sediments of lakes: Jeziorak, Jeziorak Maly and Tynwald. The greatest amounts of them were found in demersal water and in bottom sediment surface stratum. However, the percentage share of chitinolytic bacteria proved greater in deep water (9.35%) than in bottom sediments (2.16%). Surface water and the part just over the sediment contained most chitinolytic bacteria in a heavily eutrophicated lake Jeziorak Maly located in a town (11.9% and 12.6% respectively), whereas they inhabited bottom sediments in large amounts in lake Jeziorak (2.9%). The most abundant among chitinolytic bacteria were the genera of: Achromobacter, Bacillus and family of Enterobacteriaceae.