Some demonstrative embodiments of the invention include a method, device and/or system illumination-based disinfection. A disinfector may include, for example, a conduit to carry a flowing medium to be disinfected, the conduit having an inlet to receive the medium and an outlet to discharge the medium; a flow adapter configured to adapt a flow of the medium at the inlet based on an intended spatial distribution of flow velocities of entities suspended in the medium along a plurality of intended flow paths from the inlet to the outlet; and at least one illumination source to illuminate the conduit with light having a customized spatial light flux distribution, which is based at least in part on the intended distribution of flow velocities. Other embodiments are described and claimed.