Two-phase flaw in an RDC column is investigated with the methods of Computational Fluid Dynamics. An advanced model allows for the detailed description of the essentially miltidimensional dispersed liquid-liquid flaw in the extraction column. As the result of the hydrodynamics calculation velocity fields and the local distribution of volume fraction (holdup) for both phases are obtained. Deeper understanding of the extraction process can be gained from these informations. Furtheron, the results of the multidimensional flow calculation may be used to compute global quantities like Sherwood numbers or dispersion coefficients. Thus the multidimensional approach can give both insight lt in the details of the flaw and supply information required in the "classical" one-dimensional methods of column design.