To examine the cognitive processing differences in chronic and episodic pain sufferers, auditory event-related potentials (P300 or P3) were recorded in two consecutive trials from 23 chronic lower back pain patients, 22 episodic tension-type headache sufferers, and from 23 age- and sex-matched healthy persons. P3 latency and amplitude showed no difference between groups at first trial. Considering P3 latency habituation, healthy controls and episodic tension-type headache sufferers showed a significant change of P3 latency whereas lower back pain sufferers failed. Comparing the amount of habituation lower back pain sufferers stood clearly apart from healthy controls. Although there was a remarkable increase of P3 latency in episodic tension-type headache sufferers, the amount of habituation was not statistically different than it was in lower back pain sufferers. Significant P3 amplitude habituation was observed only in healthy controls. Actually, episodic tension-type headache sufferers also showed some degree of habituation, which was not statistically remarkable. The amount of amplitude habituation was not different between groups. No correlation was observed between P3 habituation and age, disease duration and symptom severity. These results may point to a disturbed attentional processing in chronic pain sufferers. Our findings suggest that in spite of a similar cortical information processing, the neurocognitive networks related with decision making and memory processing seem to work differently in chronic pain sufferers from those in episodic pain sufferers in repeating tasks. Taking into consideration the reported P3 habituation abnormalities in chronic migraine patients we can say that not the location of pain but rather its temporal pattern may have a role in disturbed attentional processing. (C) 2002 European Federation of Chapters of the International Association for the Study of Pain. Published by Elsevier Science Ltd. All rights reserved.