Extractive distillation processes are investigated by optimization. The proposed MINLP model and optimization tool are able to analyze complex distillation processes. Application of the method is demonstrated on two different extractive processes: acetone/methanol mixture using water as heavy solvent and ethanol/water mixture using methanol as light solvent. The two systems are analyzed separately; the analysis is performed both from technological and economical aspects. The optimal structures are found widely independent of the weights of different cost parts. Thus, small changes in the economic environment will not alter the optimal configuration.