The device relates to a method and a device (10) for determining an irradiation plan for a particle irradiation unit (20). In the method, a target volume (6) within a test object (14; 18) is irradiated with a particle beam (16) using the particle irradiation unit (20) according to the irradiation plan. The radiation plan is determined in order to apply the energy of the particle beam (16) according to a predetermined dose distribution in the target volume (6), the target volume (6) and the predetermined dose distribution being pre-set. When determining the irradiation plan, irradiation duration is also taken into account, the irradiation plan being determined such that the irradiation duration is as short as possible.