The study of cognitive functions is a major challenge of the modern functional imaging. Activation of specific cerebral area is obtained from the observation of physic characteristic affected by changes occurring in the blood flow resulting from an increased metabolic consumption. In this work two imaging techniques are used, the functional magnetic resonance (fMRI) and the near infrared spectroscopy (NIRS), in order to assess cerebral performance during the execution of a well known sustained attention task, the Conners' continuous performance test (CPT). With fMRI analysis were found activations in the frontal, parietal and supplementary motor areas, whereas NIRS system showed a region-wise difference in the variations of parameters and different activation trend localized in the middle-right frontal area. The combined analysis of the two techniques allows to obtain more detailed information and places itself as a first step toward a result of multimodal image integration.