The potential of CO2 sequestration by forests is characterized. It was shown on the example of Poland that it is possible to increase the CO2 sequestration by forest through afforestation of poor soils that do not guarantee profitable agricultural production, fertilisation with mineral fertilisers to increase photosynthesis process and by growing catch crops cultivated between the rows of trees. It would allow to increase in Poland the CO2 sequestration from 26.2 mln t CO2 yr-1 to about 314.4 mln t CO2 yr-1.