The type of paper used in the inner layers of cardboard has characteristics similar to test liner paper, such as resistance to moisture and the inherent strength of the paper fibers. However, it does not require the proper smoothness for printing or the coating with de-inked fibers for whitening or printing purposes, among others. This paper can be made from 100% recycled fibers, but from a hygiene perspective, it must meet acceptable standards, as in some cases, contact with food products could lead to unpleasant odors and spoilage of the items.

The papers used in the middle layers of five-layer and seven-layer cardboard are of the same type. In these cases, their role is primarily to connect and add volume. Most domestic paper factories produce this paper for cardboard manufacturing purposes.