By describing business processes in BPEL (Business Process Execution Language) one can make them executable. Then a problem arises how to assure that some non-functional requirements concerning e.g. performance of these processes, are met. In the paper a transformational approach to design of business processes is presented. To check equivalence of business processes resulting from the transformations, a BPEL description is converted to Process Algebra (Lotos version) and model-checking techniques are applied. The paper contains also an example of applying the proposed approach in a real-life situation.