During a two-year investigation of the Úpské rašeliniště peat bog and the Pančavské rašeliniště peat bog in the Krkonoše Mts (Czech Republic) about 228 taxa of cyanobacteria and algae were found. The diatoms were the dominant group in most of the investigated samples. The relationship between algal flora and the environmental characteristics of the pools was studied. The pH, shading and type of bed were most important factors influencing algal communities in the pools.