A method for producing a microfluidic system, containing at least one microfluidic component having at least one microfluidically active surface is disclosed. The method includes providing a microfluidic composite substrate having a connection side, comprising at least one microfluidic component introduced into a polymer composition, wherein the microfluidically active surface of said component forms a part of the connection side of the microfluidic composite substrate. The method further includes providing a mating substrate having a connection side for connection to the microfluidic composite substrate. Also, the method includes providing microfluidic structures at least on the connection side of the composite substrate and/or on the connection side of the mating substrate at least for the purpose of forming a microfluidic channel structure in the microfluidic system. In addition, the method includes connecting the microfluidic composite substrate and the mating substrate by their connection sides to form a microfluidic channel structure.