A printing unit of a printing press, such as a web press constructed as a periodical printing press, having at least one printing couple, wherein the printing couple or each printing couple comprises a form cylinder, a transfer cylinder, an inking unit, and preferably a dampening unit. A drive motor is associated with at least one printing couple, and drives the form cylinder or the transfer cylinder of a respective printing couple. In accordance with the invention, a flywheel mass is associated with at least one drive motor which drives the form cylinder or the transfer cylinder of the respective printing couple, where the flywheel mass is connected to the rotor of the respective drive motor in a torsionally rigid manner.