A trim structure intended on one hand to receive a door, in particular an internal door, and on the other hand to be joined to a partition. The structure includes two lateral walls facing one another and spaced apart by a thickness. The thickness being adjusted with respect to the thickness of the partition such that the lateral walls form an external surface that is flush with the external surface of the partition when the structure is joined to the partition. A transverse end wall connects the two lateral walls. The transverse end wall includes a planar surface that is configured to butt up against the thickness of a vertical edge face of the door and a projecting element forming a bearing surface for the door. The walls being formed from at least one composite panel, the panel comprising a central layer sandwiched between two facing layers.