In our prototype, we define a shared screen space between two collaborating users. Content sharing through a S3D UI design utilizing stereoscopy as a fundamental element of the design is, to best of our knowledge a novel approach, whereas earlier research has introduced mobile content sharing through a shared screen space using other techniques. Winkler et al. [8] have demonstrated a concept, where mobile content is shown and shared during a phone call with the help of phone integrated picoprojector and gesture recognition. The user is able to interact with the projected interactive surface with his other hand and share part of the projected screen with the other person in the call. Similarly to [8], we organize the UI layout so that two users sharing content with each other can both see a common part of the screen. However, the shared screen area is not defined in the (x,y) plane on the screen, but at a defined depth enabled by stereoscopic UI. In the photo sharing application, each mobile device has two UI layers; a private layer, that shows the content visible only to the user of the device, and a shared layer for shared content. The private layer is situated on the screen surface level, i.e. having zero disparity (zero parallax). The objects placed on the shared layer appear behind the screen level, i.e., with positive parallax/disparity, and seem to be located deeper than the objects on the private layer. The shared layer was chosen to appear at greater depth, as it was seen to be situated further from the user him/herself, and towards the other user(s). In addition, Mizobuchi at al. [5] have recommended that in a reading task, the object of primary interest should be presented on screen level, which here is the user’s own content.