This paper is based on the findings from the project funded by the Ministry of Science and Higher Education of Poland. It presents the application of value stream mapping in supply chains and some inadequacy of this method for supply chain integration. Based on the findings, a new Supplier Customer Production process Integration SCPI methodology is proposed. The paper presents problems with integration of companies within the lean supply chain. Usually separate actions are undertaken by the companies within the same supply chain to implement lean management philosophy for production systems and external logistics processes. These isolated activities may lead to pushing inventories from one supply chain partner to another instead of reducing them. To reduce inventories along the supply chain the new approach of production and logistics process improvement needs to be applied. The new concept must take into consideration influence of local improvements in one plant on other cooperating enterprises as well as on the logistics system between them.