There is proposed a device for the slice-by-slice irradiation of tumour tissue (3) in a patient using a particle beam, having—an accelerator (7) for generating a particle beam (5) with predetermined energy for each slice, —a raster scanning device (9), acting on the particle beam (5), for the slice-by-slice scanning of the tumour tissue (3), —a modulator (17) for modulating the energy of the particle beam (5), —a detection device (37) for the time-resolved detection of the position of the tumour tissue (3) and having—a first storage device for storing data relating to the tumour tissue (3), which were determined prior to the irradiation operation, and for releasing that data to the raster scanning device (9) and to the modulator (17). The device is characterized by—a module (39), which registers the data on the course of the irradiation and the data of the detection device (37) which have been obtained during an irradiation operation.