Abstract: Apparatus and method for monitoring the width of the transverse sealing web of a sealed, cut package unit in which products are packaged and which is transported further in a cyclic or continuous manner in the longitudinal direction. Two laser-optical sensors are arranged opposite one another above and below the cut package units. The measured values of the sensors, the said measured values corresponding to the distance from the package unit, are acquired at a speed-proportional clock frequency. A difference value is formed from the measured values of the two sensors which have been recorded in the same clock cycle, and an output signal is generated if the number of successive difference values which exceed or fall below a predetermined reference value falls below a predetermined critical value.