Abstract: In controlling the thickness of a moving web of material, after it passes through a production station containing a final control element for its thickness, it is moved past a radiometric device which measures the weight of the web per unit area. Downstream from the radiometric device, the web is moved past an optoelectronic device utilizing laser radiation for measuring the thickness of the web. The two measurements are compared and the radiometric device measurement is corrected based on the optoelectronic device measurement and the comparative corrected value is transmitted to a control unit which actuates the final control element in the production station. Preferably, the optoelectronic device is spaced from the production station so that it is out of the range of any significant environmental influences.