Cavitating flows in rocket engine turbo-pump inducers are studied by experimental and numerical ways. The experimental analysis focused on the cavitating structures at the periphery of the inducer, the quantification of the vapour volume at inducer inlet, its relation with the backflow and the obstruction effect on the main flow. A 2D numerical model of unsteady cavitation was applied to a blade cascade drawn from the inducer geometry. Unsteady behaviour of sheet cavities attached to the blade suction side depends on the flow rate and cavitation number. In certain conditions, a rotating cavitation phenomenon is observed, in good agreement with experimental observations.