Conflicting data on cognitive defects in migraine could be explained by differences in the clinical variables of the populations studied. We investigated 21 patients with migraine with aura and 24 with migraine without aura, diagnosed according to the International Headache Society criteria. The patients were submitted to a comprehensive battery of neuropsychological tests and grouped according to attack frequency and side of pain. Attack frequency was not associated with significant differences in any of the tasks, while location of pain was found to be significantly related to poorer performance on both the immediate and delayed recall of Rey Complex Figure in migraineurs both with and without aura, and a significant relationship between side of pain and number of clusters in the second trial of California Verbal Learning Test was found only in migraine with aura patients. The finding of worse performances in patients with right-sided pain seems to support a right hemisphere dysfunction hypothesis.