At the moment ion exchanger resins display the highest binding capacities for proteins. Polymeric surface modification methods utilize the full pore space and allow to guarantee high capacities for small as well as for large proteins. Capacity maximization is also possible by pore size optimization fitting the pore size to the molecule size without loosing a lot of dynamic binding capacity under current process conditions. Further improvements of resins can be achieved by optimizing the pore structure and pore volume, which could enhance the mass transfer and so the dynamic binding capacity.