The paper presents results of studies on posssibilities to use hydrocarbon (oil and gas) deposits as underground sites for storage of CO2 in Poland. The analyses covered 337 oil and gas deposits from the areas of the Polish Lowlands and Carpathian Mountains and their foreland to show that geological conditions prevailing over vast areas in Poland are favorable for CO2 storage in oil and gas deposits. However, only a few of these deposts are found to be suitable for this purpose when their exploitation ends. Two such oil deposits and 10 gas deposits have been selected. Extractable original reserves of the deposits recognized as suitable for underground CO2 storage are estimated at about 47,116,400 tonnes of oil and 189,034 million cu. m of gas, which equals 46% and 56% of extractable original reserves of oil and gas, respectively. The distance between a source of CO2 emissions and a potential underground storage site is shown to be one of the criteria which will bear a decisive influence on the order in which the sites are selected for use as underground CO2 storage sites.