Mixed reality (MR) integrates virtual content with the physical world, enabling users to place virtual objects in real environments and interact with or observe them. As MR technologies advance, such experiences are becoming increasingly common. However, it remains unclear how the visual and interactive representation of virtual objects influences users, and few studies have examined users’ behavioral responses to virtual objects. We investigated whether representation factors (interactivity, transparency, and size) affect users’ sense of presence and their behaviors toward the object (e.g., avoidance or displacement). Here, interactivity refers to whether users can touch the virtual object. In two experiments (desk-scale and room-scale) conducted, participants performed a reaching task toward a real target located behind a virtual object whose representation factors were manipulated. Presence and behavior were assessed using subjective ratings and objective measures from tracking data and video observations. Perceived presence varied with interactivity, transparency, and size, whereas avoidance and displacement behaviors showed no reliable differences across conditions. Nonetheless, the results suggest that behavioral responses may emerge when interaction demands are stronger or the scale of interaction is larger. Overall, representation affected perceived presence but did not reliably change avoidance or displacement behavior in this task.