A computer-implemented medical method for setting up a patient for radiotherapy, the method comprising the following steps: a) free-breathing data is received at a computer and from a device adapted to provide the free-breathing data, wherein the free-breathing data describes an image or CT-dataset describing the spatial position of a section of an outer contour of the patient's body in a free-breathing state; b) DIBH data is received at the computer and from a device adapted to provide the DIBH data, wherein the DIBH data describes a planning CT-dataset of the patient in a state of a deep-inspiration-breath-hold (DIBH), describing the spatial position of the outer contour section and of a target structure of the patient, which is to be irradiated, in the state of the deep-inspiration-breath-hold (DIBH); c) registration data is determined by the computer and based on the free-breathing data and the DIBH data, describing the spatial position of the target structure in the state of the deep-inspiration-breath-hold (DIBH) as a function of the spatial position of the outer contour section in the free-breathing state, wherein the image or CT-dataset is registered with the planning CT-dataset; d) isocentre data is received at the computer and from a device adapted to provide the isocentre data, wherein the isocentre data, describes the spatial position of an isocentre of a radiation treatment apparatus; e) positioning data is determined by the computer and based on the registration data and the isocentre data, describing a spatial position of the outer contour section in the free-breathing state, for which a spatial position of the target structure in the corresponding state of the deep-inspiration-breath-hold (DIBH) aligns with the spatial position of the isocentre of the radiation treatment apparatus. a) free-breathing data is received at a computer and from a device adapted to provide the free-breathing data, wherein the free-breathing data describes an image or CT-dataset describing the spatial position of a section of an outer contour of the patient's body in a free-breathing state; b) DIBH data is received at the computer and from a device adapted to provide the DIBH data, wherein the DIBH data describes a planning CT-dataset of the patient in a state of a deep-inspiration-breath-hold (DIBH), describing the spatial position of the outer contour section and of a target structure of the patient, which is to be irradiated, in the state of the deep-inspiration-breath-hold (DIBH); c) registration data is determined by the computer and based on the free-breathing data and the DIBH data, describing the spatial position of the target structure in the state of the deep-inspiration-breath-hold (DIBH) as a function of the spatial position of the outer contour section in the free-breathing state, wherein the image or CT-dataset is registered with the planning CT-dataset; d) isocentre data is received at the computer and from a device adapted to provide the isocentre data, wherein the isocentre data, describes the spatial position of an isocentre of a radiation treatment apparatus; e) positioning data is determined by the computer and based on the registration data and the isocentre data, describing a spatial position of the outer contour section in the free-breathing state, for which a spatial position of the target structure in the corresponding state of the deep-inspiration-breath-hold (DIBH) aligns with the spatial position of the isocentre of the radiation treatment apparatus.