There is provided a back rest of a motor vehicle seat, which comprises a back rest support (26), onto which a shoulder rest (36) for a separate adjustment of an upper section of the back rest is provided, whereby the shoulder rest (36) is linked to the back rest support (26) and that an adjustment device is allocated to it, which is embodied as an air bag (46), which can be filled and emptied in a controlled manner and which is arranged between the back rest support (26) and the shoulder rest (36) and that re-adjusting device are provided, which are arranged between the shoulder rest (36) and the back rest support (26) and which stress the shoulder rest (36) in one of its two extreme positions, for example the position of the smallest distance from the back rest support (26).