The Simon Effect (SE) (faster and more accurate responses in presence of correspondence between the task-irrelevant position of the stimulus and that of the effector) has been consistently observed along the horizontal and vertical planes while little is known about the existence of the SE on the z-plane. Twenty-four participants performed a Simon task with 3D images and in-depth arrangement of the response keys. Results indicated a main effect of 3D space, but the absence of SE along the z-plane. We discuss possible limitations of our study and encourage future research to further evaluate the presence of SE in depth.