Space perception is a multimodal construct, and recent evidences have suggested that action and body representation were contributing to spatial cognition. For example, space is thought to be subdivided into different subspace realms calibrated to body size and proportions (Previc, 1998). Moreover, spatial cognition seems to beneficiate from action simulation processes when visually perceiving if an object is within reachable space (Coello & Delevoye-Turrell, 2007). Others believe that when estimating the distance between an observer and a target, the effort required to attain the target can moderate distance estimation (Proffitt, 2006; Witt & Proffitt, 2008). In the two studies presented here we investigated how a motor dual task (experiment 1) and how action observation in different postural contexts (experiment 2) could moderate both reachability judgment and distance estimation spatial tasks. In the first experiment, we observed that hand movements slowed down participant’s responses when evaluating reachability and estimating egocentric distances but not when estimating allocentric distances (i.e., length). Suggesting that the motor dual task interfered with action simulation processes implied in egocentric space perception. In the second experiment, participants had to judge the reach capacities of an actor presented from a third person view but also estimate the distances separating the actor from objects. We investigated how two different postures of the actor and how observing this actor performing reaching action could moderate participant’s responses. Results showed a significant influence of actor posture in both tasks. Moreover, after observing actor’s reaching actions, participant’s responses in both tasks were more accurate.