An arrangement for facilitating the mounting of printing plates on a plate cylinder of an offset printing machine. Two arms are mounted atop the machine at the opposite lateral sides thereof and have free ends provided with hooks. A rail is suspended from these hooks and carries quick-coupling devices which engage the trailing edge of a printing plate to be mounted. The hooks are suspended on ropes which are wound upon rollers mounted on the free ends of the arms; turning of the rollers in a sense causing unwinding of the ropes is resisted by torque springs or similar devices; this resistance can be varied to compensate for printing plates of different weights. Thus, the weight of the printing plate cannot cause the ropes to unwind; however, when the leading edge of the printing plate is connected to the plate cylinder and the cylinder is slowly rotated to take the plate up on it, the pull exerted by the cylinder causes unwinding of the ropes.