The relation between a paper-pencil test of sustained attention (d2-letter cancellation test, d2-LCT) and the contingent negative variation (CNV) as a cortical slow potential was calculated in 23 healthy undergraduate students. Both d2-LCT and CNV reflect selective, focussed attention. There was a Pearson correlation coefficient of r = -0.670 between the early component of the CNV and the number of checked letters in d2-LCT, indicating significant differences in early CNV between low and high performance in d2-LCT. The results showed a linear relationship between paper-pencil registered attentional properties and the cortically recorded early component of CNV.