The phytoplankton of nine lakes located in different types of landscapes in the southern part of the Republic of Karelia was studied in spring and summer seasons of 20112012. In seven of the lakes phytoplankton was studied for the first time (lakes Gizhozero, Lelikozero, Myagrozero, Kondozero, Korytovo (Zaonezhsky Peninsula), lakes Koverjarvi, Rapsudozero (Vendyurskaya group). The highest species diversity in lakes of all types of landscapes was demonstrated by diatoms (20-42 % of the total number of species) and green algae (17-42 %). Each lake had its specific algal flora, and degree of their similarity measured by the S0rensen index was low. Quantitative indicators of phytoplankton in the lakes varied over a wide range of values. Phytoplankton abundance ranged within 5.8-1060.5 thousand cells/L (with an average of 160.1 ± 29.1), and biomass ranged from 0.010 to 1.374 g/m3 (0.209 ± 0.04 g/m3 on average). Data clustering using 26 variables showed different levels of relationship both between lakes and between their groups. It was found that the main factors influencing the total abundance and total biomass of phytoplankton, as well as the abundance and biomass of different groups of algae are the catchment area/water surface area ratio, total nitrogen and phosphorus, water catchment area, mineralization, lake surface area, pH and color. We obtained significant positive correlations (at a level of p < 0.05) between the structural indicators of phytoplankton and nutrients (total nitrogen and phosphorus).