Abstract: A method for projecting a user interface of an application program provided for a screen of a mobile device is provided onto a screen of an infotainment system arranged in a vehicle. The user interface can be displayed in a manner suitable for the driver of the vehicle if the screen size of the infotainment system is determined in the infotainment system. The screen size is transferred to the mobile device via a data interface, the user interface size of the application program running in the mobile device in the unit of the comparable size is determined in the mobile device. The screen size of the infotainment system is compared with the user interface size of the application program and a decision is made on the basis of the comparison, which image data is transferred from the mobile device to the infotainment system via the data interface.