An anti-theft device comprising a flexible cable provided with two conducting wires which are mutually connected in order to close an electrical contact and are connected, at a first end, to a control unit designed to act in response to the opening/closure of the electrical contact, characterized in that the flexible cable is connected, at the second end, to means for detachable connection to at least one item to be restrained, the detachable connection means comprising security means of the mechanical type which are adapted to prevent the opening of the detachable connection means, a deactivation device being provided which can engage the detachable connection means in order to open the security means.