Previous studies have reported that deficits in attention are often a common complaint in individuals suffering from pain and attentional impairment in patients with pain has been demonstrated on a variety of neuropsychological measures. Much of the research to-date, however, has not taken into account extraneous factors that may contribute to observed cognitive deficits. Using the California Verbal Learning Test - II, attention and memory performance was examined in two clinical populations (pain and mild traumatic brain injury) while controlling for effort using the Word Memory Test. Controlling for effort led to different explanations of poor performance on attention variables. While mild deficits were expected, and could be accounted for by psychological factors (i.e. somatization), extremely poor performance was more likely related to poor effort. The findings of this study strongly support the necessity of measuring effort during neuropsychological and pain psychological evaluations.