A radiation imaging system is provided. The system comprises: an imaging unit including a plurality of pixels configured to generate a radiation image and a detection unit configured to detect incident radiation to perform exposure control； an irradiation control unit configured to control radiation irradiation by a radiation source, an obtainment unit configured to obtain a delay time of communication between the imaging unit and the irradiation control unit； and a determination unit. The determination unit determines, based on a radiation irradiation condition set by an operator and the delay time obtained by the obtainment unit, whether to permit imaging by exposure control using a signal output from the detection unit.
