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The objective of this study is to determine the usefulness of results of hydrological observations (1961-2015) carried out in a deep lake for the assessment changes in the ice-thermal regime of a shallow lake. The paper is based on results of daily values of surface water temperature and ice phenomena in shallow Lake Lebsko and deep Lake Charzykowskie. Similar, statistically significant, positive trends of water temperature were determined in both lakes (0.26 degrees C 10 year(-1) in Lake Lebsko and 0.25 degrees C 10 year(-1) in Lake Charzykowskie). The fastest increase in mean monthly water temperature in the analysed period (1961-2015) occurred in May (3.37 degrees C in Lake Charzykowskie) and April (2.76 degrees C in Lake Lebsko). The majority of elements of the thermal regime of surface waters in shallow lakes were generally determined to be similar to the same elements in deep lakes, and the effect of climatic changes on the thermal regime of both lakes was found to be similar. Less similarity is observed between elements of the ice regime, particularly in date of decline of the ice cover.