A radiation imaging system includes an imaging unit, a detection unit, a change determination unit and a control unit. The imaging unit emits radiation and images a dynamic state of a subject, thereby taking a plurality of frame images of the dynamic state of the subject. The detection unit detects the dynamic state of the subject being imaged and generates detection information on the dynamic state. The change determination unit determines whether change of the dynamic state being imaged is within a predetermined range based on the generated detection information. The control unit controls capturing of the taken frame images according to a result of the determination of the change determination unit.