An adsorbent for whole blood in the form of essentially spherical non-aggregated particles. The adsorbent comprises a porous carrier material having an average pore size of ≦1.5 μm, whereby a maximum of 50% of the pore volume may be in pores having a pore size of >1.5 μm, whereby the outer surfaces of the porous carrier material have at least one surface modification M1 so that the outer surface essentially does not interact with blood cells, and the inner surfaces of the porous carrier material, e.g., the surfaces of the pores of the porous carrier material, have at least one surface modification M2 which interacts with substances present in blood.