A closure device for attaching to a packaging container, by which the container is closable but cannot be opened by children once closed. The closure device is made of at least 70% paper-based material and includes a tab receptacle, a receiving space and an insertion tab with a hook element. To close the device, the insertion tab is inserted in the receiving space of the tab receptacle and a free end of the hook element lockingly engages with an edge of the space. To open the closure device, the insertion tab is withdrawn from the receiving space while applying pressure to the hook element to release locking. For this purpose, an opening is formed in a wall of the tab receptacle through which pressure is applied. An item of packaging composed of the packaging container, includes a removal opening and the closure device.