A system (1) for additive manufacturing of three-dimensional objects, comprising one or more working stations (21), which are provided for performing at least one working process in the additive manufacturing of three-dimensional objects, at least one freely positionable mobile storage unit (2) comprising a rack-like storage device (4) comprising at least one storage room (5) provided for storing at least one powder module (6), especially for the purpose of conveying the powder module (6) between different working stations (21) of the system (1), and at least one driverless, freely movable mobile conveying unit (3) comprising a receiving device (12) provided for receiving at least one mobile storage unit (2) for the purpose of conveying the storage unit (2) between different working stations (21) of the system (1).