This paper presents theoretical model and experimental results on radiation heating and thermally induced distortions in x‐ray masks. The temperature rise of the mask membranes during x‐ray irradiation was measured using metal resistors fabricated directly on the mask. A method was developed to calculate thermal wave effects: thermal distortions of the printed image due to the nonuniformity of temperature distribution in the mask membrane during scanning of the x‐ray beam. Experimental results for the thermal wave effects are presented; they indicate that the effects are noticeable only during operation in a vacuum environment. The effects are negligible during normal operation in a helium atmosphere.