Due to increasing demands on pure products, there is a rapid growth of interest in chromatographic techniques. Those techniques are able to separate even compounds with small differences in their physico-chemical properties. Continuous processes, e.g. simulated moving bed (SMB) chromatography, are a new field of growing interest for the production of pure pharmaceuticals and fine chemicals. These complex procedures cannot be optimized by a strategy based on trial and error. Therefore, rigorous modeling and efficient simulation/optimization techniques have to be used. This article presents an overview showing the advantages and disadvantages of different modeling approaches in theory and in practical applications to technical chromatographic separations.