A chassis which is suitable for supporting a child vehicle seat is provided with a frame as well as with connectors that can be detachably connected in use to securing elements that are present in a vehicle. The chassis is further provided with an unlocking mechanism for releasing the engagement between the connector and the securing element. The chassis is provided with a slide for supporting the child vehicle seat, which slide is movable with respect to the frame from a first position, in which the slide is positioned at a relatively large distance from the connector, to a second position, in which the slide is positioned closer to the connector. The slide is locked against movement from the second position to the first position when at least one connector is connected to the securing element.