The invention relates to expandable styrene polymers containing a) a styrene polymer, b) and at least one carbon dioxide absorber, mixed or copolymerized with the above, in an amount of from 0.01 to 50% by weight, based on the sum of a) and b), and c) a blowing agent or blowing agent mixture in an amount of from 0.5 to 12% by weight, where the blowing agent or blowing agent mixture comprises c1) from 10 to 100% by weight of carbon dioxide and c2) from 0 to 90% by weight of at least one further blowing agent. The invention furthermore relates to the styrene polymers containing a carbon dioxide absorber, to the styrene polymer foams obtainable from the expandable styrene polymers, and to an improved process for impregnating styrene polymers with carbon dioxide-containing blowing agents or blowing agent mixtures.