OBJECTIVE: This study aimed to examine cognitive functioning in postpolio syndrome (PPS) after controlling for the effects of depression and illness behavior. BACKGROUND: Few studies have investigated the possible cognitive sequelae of PPS, despite widespread documented subjective complaints of "mental fatigue." METHOD: A total of 23 PPS sufferers, 20 polio survivors without PPS, and 22 matched controls were compared using the Beck Depression Inventory-II; the Illness Behaviour Questionnaire; a chronic fatigue syndrome symptom checklist; and several measures of memory, attention, and concentration, including the Brown-Petersen Task, Stroop Test, Austin Maze, California Verbal Learning Test, Trail Making Test, Controlled Oral Word Association Test, and Symbol-Digit Modalities Test. RESULTS: In those participants with a medically confirmed diagnosis of PPS, there was a significantly higher level of depressive and hypochondriacal symptomatology as compared with the other two groups. Nevertheless, no significant differences existed between the three groups on neuropsychological measures. CONCLUSIONS: These results indicate that the attention and memory difficulties reported by PPS sufferers may be linked to the physical or psychological manifestations of the illness rather than to objective decrements in cognitive performance.