Disclosed is an implantable device (1) to be used in a human and/or animal body for occluding or partially occluding defective openings, hollow spaces, organ tracts etc. for creating a defined connecting opening between walls, organs hollow spaces, etc. Said implantable device (1) comprises a support structure which has a great length-to-width ratio along an axis (63) in a first operating state (primary shape) while having a smaller length-to-width ratio along said axis (63) in a second operating state (secondary shape). The support structure is provided with a proximal (20) and a distal section (30) and is formed from a single wire-type element (10) by intercoiling and/or intertwining and/or interweaving like a tissue and/or a cluster and/or a net. Also disclosed is a placing system especially for such an implantable device, comprising an advancing element (5), a directing wire (6,9) and/or an inner mandrin, and at least one holding wire (80,81). The directing wire (6) and the at least one holding wire (80,81) are used for cooperating with a proximal end of the implantable device (1), the implantable device (1) being transformable from a primary shape into a secondary shape and vice versa by moving the holding wire (80, 81) and the directing wine (6) relative to the advancing element (5).