It is well known that humans and other animals can exploit the probabilities of events occurring at different spatial locations to covertly guide attention. However, attentional shifts observed before saccadic eye movements seem to rely on different mechanisms than those observed during covert spatial attention. In this study, we investigated if presaccadic attentional shifts are modulated by the probability of spatial cues. Nineteen participants performed a visual orientation discrimination task in which a central cue indicated the location of a target stimulus with four different probabilities (88, 40, 22, and 10%) in distinct blocks. Targets (clockwise or counterclockwise Gabors) were presented in an array containing three other distractors (Gaussian noise), one in each quadrant of the visual field. A response cue was used to indicate the target location after the array offset. Subjects performed two presaccadic and two covert (endogenous) attention sessions. Our results showed that target perception during covert orienting was only modulated by the spatial cues associated with higher probabilities (88 and 40%). Interestingly, we observed that under presaccadic attention, target discrimination was improved in all probability conditions, even when the probability of a target occurring at the saccade location was very low (i.e. 10%). However, the magnitude of the presaccadic perceptual enhancement also increased with spatial probability. Together, our findings suggest that presaccadic shifts of attention might consist of two processes, one automatic and evident in the perceptual enhancement of low-probability targets, and the other voluntary and modulated by top-down attentional goals.