The aim of this work was to characterise morphologically and ecologically 4 new species of diatoms to Poland (Aulacoseira tenella, Eunotia galica, Pinnularia subfalaiseana, and Psammothidium scoticum) together with the location of their occurrence in the Janowskie forests and Turzaski forest in southeastern Poland. The research material from Turzański forest were collected in the in spring and autumn 2023 in a forest pond and a small stream flowing out of this pond, while in the Janowskie Forests always in spring season of 2023 and 2024. The results showed that the samples were characterized by an acidic or weakly acidic reaction (pH 4.0-6.4) and low electrolytic conductivity values (40-134 S cm-1). Studies conducted in forest water ponds and streams flowing from them have confirmed that such places are habitats of diatoms new to Poland, often known only from a few locations in Europe.