Method for assisting with the installation of at least one actual screen for a presence detector that is arranged in at least one zone to be monitored, the presence detector comprising at least one passive infrared sensor that is provided with at least one optical element and a camera having a predetermined position relative to the position of the passive infrared sensor, the method comprising at least the following steps: - an imaging step, in which step at least one image of the zone to be monitored is photographed or filmed by the camera, - a step of displaying an overlay, in which step an overlay comprising a plurality of regions that are representative of detection beams of the passive infrared sensor is displayed by first display means on the basis of a signal to display an overlay that is prestored in a memory (9, 11) for storing the overlay and that is transmitted from the memory (9, 11) for storing the overlay to said first display means and in which step said image of the zone to be monitored is transmitted from the camera to the first display means and is displayed by the first display means, such that said image of the zone to be monitored and said overlay are superposed, - a selection step, in which step at least one of the regions of the overlay is selected by selection means (19, 19') and data that are representative of said at least one selected region of the overlay are stored in a memory of a computer (12, 12'), - a step of determining the form of a virtual model of a screen, in which step the computer (12, 12') determines, on the basis of the data that are representative of said at least one selected region of the overlay, a display signal that is representative of the form of a virtual model of a screen in a configured state and stores the display signal that is representative of the form of a virtual model of a screen in a configured state in the memory of the computer (12, 12'), - a step of displaying the virtual model of a screen, in which step a virtual model of a screen in a configured state is displayed by second display means on the basis of the display signal that is representative of the form of a virtual model of a screen in a configured state and that is transmitted to the second display means from the memory of the computer (12, 12'), - a step of configuring the actual screen, in which step an actual screen in a configured state is formed at least on the basis of the virtual model of a screen in the configured state by configuration means, - a step of installing the actual screen, in which step the actual screen in the configured state is arranged over said at least one optical element of the passive infrared sensor by an operator. - an imaging step, in which step at least one image of the zone to be monitored is photographed or filmed by the camera, - a step of displaying an overlay, in which step an overlay comprising a plurality of regions that are representative of detection beams of the passive infrared sensor is displayed by first display means on the basis of a signal to display an overlay that is prestored in a memory (9, 11) for storing the overlay and that is transmitted from the memory (9, 11) for storing the overlay to said first display means and in which step said image of the zone to be monitored is transmitted from the camera to the first display means and is displayed by the first display means, such that said image of the zone to be monitored and said overlay are superposed, - a selection step, in which step at least one of the regions of the overlay is selected by selection means (19, 19') and data that are representative of said at least one selected region of the overlay are stored in a memory of a computer (12, 12'), - a step of determining the form of a virtual model of a screen, in which step the computer (12, 12') determines, on the basis of the data that are representative of said at least one selected region of the overlay, a display signal that is representative of the form of a virtual model of a screen in a configured state and stores the display signal that is representative of the form of a virtual model of a screen in a configured state in the memory of the computer (12, 12'), - a step of displaying the virtual model of a screen, in which step a virtual model of a screen in a configured state is displayed by second display means on the basis of the display signal that is representative of the form of a virtual model of a screen in a configured state and that is transmitted to the second display means from the memory of the computer (12, 12'), - a step of configuring the actual screen, in which step an actual screen in a configured state is formed at least on the basis of the virtual model of a screen in the configured state by configuration means, - a step of installing the actual screen, in which step the actual screen in the configured state is arranged over said at least one optical element of the passive infrared sensor by an operator.