Abstract <p>Hydrochemical characteristics of small lakes typical for different landscapes of the Republic of Karelia have been compiled based on statistical estimates. The test sample to be studied was formed based on hydrochemical data on the 223 most studied small lakes of Karelia, which were grouped by landscape type. The possibility of identifying atypical (anomalous) lakes for a certain area, including unique lakes, has been assessed using statistical criteria for identifying outliers during the analysis of hydrochemical data. The search for anomalous values was based on classical methods of statistical analysis, including quantile analysis (box plot) and the statistical Chauvenet and Rosher (Thompson’s) criteria for searching for outliers. The efficiency of using these methods to identify anomalies has been assessed. An expert analysis of the resulting sample of lakes with anomalous values of hydrochemical parameters has been performed to identify the pattern and causes of anomalies and determine the uniqueness of the lakes. Paths for further research into the possibility of using mathematical statistics methods to search for anomalies and further development of criteria for the hydrochemical uniqueness of lakes are outlined.</p>