Although we intuitively believe that salient or distinctive objects will capture our attention, surprisingly often they do not. For example, drivers may fail to notice another car when trying to turn or a person may fail to see a friend in a cinema when looking for an empty seat, even if the friend is waving. The study of attentional capture has focused primarily on measuring the effect of an irrelevant stimulus on task performance. In essence, these studies explore how well observers can ignore something they expect but know to be irrelevant. By contrast, the real-world examples above raise a different question: how likely are subjects to notice something salient and potentially relevant that they do not expect? Recently, several new paradigms exploring this question have found that, quite often, unexpected objects fail to capture attention, a phenomenon known as 'inattentional blindness'. This review considers evidence for the effects of irrelevant features both on performance ('implicit attentional capture') and on awareness ('explicit attentional capture'). Taken together, traditional studies of implicit attentional capture and recent studies of inattentional blindness provide a more complete understanding of the varieties of attentional capture, both in the laboratory and in the real world.