In this paper, an investigation of the behaviour of laminated veneer lumber slabs in four-point bending tests was analysed. Two types of laminated veneer lumber (LVL) are manufactured in Poland, i.e., LVL R and LVL X. In LVL R all veneers are glued together longitudinally whereas in LVL X a fifth of the veneers are glued crosswise. In this paper, the short-term behaviour, load bearing-capacity, and mode of failure of slabs made of LVL X were studied. The failure modes of the analysed slabs were associated with the delamination and cracking of veneer layers in the lower part of the slab in the tensile zone. Furthermore, the 3D finite element model was developed and verified against the laboratory test results. In the numerical model, LVL was described as an orthotropic material. What is more, Hill’s function was used to take into account the anisotropic plastic flow of LVL after reaching a yield point. The results of the laboratory tests and the numerical simulation were compared, yielding similar results.