Our previous report [Kedzior, K., Martin-Iverson, M., 2006. Chronic cannabis use is associated with attention-modulated reduction in prepulse inhibition of the startle reflex in healthy humans. J. Psychopharmacol. 20, 471-484.] indicates that chronic cannabis use in healthy humans is associated with deficits in the attentional modulation of prepulse inhibition of the acoustic startle reflex. The aim of the current study was to compare the attentional modulation of prepulse inhibition among healthy controls, otherwise-healthy cannabis users and schizophrenia patients (non-users) utilising the same attentional paradigm. Auditory startle reflex (the eye blink) was recorded from orbicularis oculi muscle while participants were attending to or ignoring 100 dB pulses and 70 dB prepulses separated by 20-200 ms. Cannabis users and schizophrenia patients showed a significant reduction in prepulse inhibition relative to controls while attending to, but not ignoring, auditory stimuli. These results suggest that the reduction in prepulse inhibition observed in cannabis users and in schizophrenia patients appears to be related to attentional dysfunction. (c) 2007 Elsevier B.V. All rights reserved.