Substantial amount of research in Psychology has studied how people manipulate objects in the physical world. This work has unveiled that people show strong signs of prospective motor planning, i.e., they choose initial grasps that avoid uncomfortable end postures and facilitate object manipulation. Interactive tabletops allow their users great flexibility in the manipulation of virtual objects but to our knowledge previous work has never examined whether prospective motor control takes place in this context. To test this, we ran three experiments. We systematically studied how users adapt their grasp when asked to translate and rotate virtual objects on a multitouch tabletop. Our results demonstrate that target position and orientation significantly affect the orientation of finger placement on the object. We analyze our results in the light of the most recent model of planning for manipulating physical objects and identify their implications for the design of tabletop interfaces.