A theoretical consideration is given of the transverse multimode generation in a laser which is equipped with a lossy layer below an active layer for mode control, e.g., the buried twin‐ridge substrate laser, the channeled substrate planar laser, and the V‐shape inner stripe laser. The multimode generation occurs as a result of the reduction of the first‐order mode threshold to the fundamental mode threshold. It is shown that even a small asymmetry of the lossy layer causes large reduction of the first‐order mode threshold.