Résumé : Multi-touch displays represent a promising technology for the display and manipulation of 3D data. To fully exploit their capabilities, appropriate interaction techniques must be designed. In this paper, we explore the design of free 3D positioning techniques for multi-touch displays to exploit the additional degrees of freedom provided by this technology. We present a first interaction technique to extend the standard four viewports technique found in commercial CAD applications and a second technique designed to allow free 3D positioning with a single view of the scene. The two techniques were then evaluated in a controlled experiment. Results show no statistical difference for the positioning time but a clear preference for the Z-technique.