In a measuring method for measuring the imaging quality of an optical imaging system (10), a measuring mask is provided, which has a mask structure (20), which can be arranged in the region of an object surface of the imaging system. Furthermore, provision is made of a reference structure (23) adapted to the mask structure, which reference structure is to be arranged in the image surface (12) of the imaging system, and a two-dimensionally extended, radiation-sensitive recording medium (24), which is arranged in a recording position in such a way that a superimposition pattern that arises when the mask structure is imaged onto the reference structure can be detected by the recording medium. For the evaluation of the recording medium, the recording medium is brought from the recording position into an evaluation position remote therefrom. The measuring method and the associated measuring system are particularly suitable for fast, high-precision measurement of projection objectives in the incorporated state in microlithography projection exposure apparatuses.