Increasing evidence suggests that a large number of distinct cortical areas and associated subcortical structures participate in the processing of visual information and that different aspects of visual scenes are evaluated in different areas. This necessitates identification of cortical and subcortical regions cooperating in particular visual tasks. Using the 2-deoxyglucose technique, we monitored the differential activation of areas in the cat visual cortex participating in an orientation discrimination and a detection task. Concordant with previous lesion studies, we found increased activity levels in area 17 in the discrimination condition relative to the detection condition. In addition, the 2-deoxyglucose technique revealed discrimination-related increased activations in the claustrum, the putamen and in parts of the anteromedial, anterolateral and posterolateral lateral suprasylvian visual areas. Regions activated differentially with the detection task comprised subdivisions of areas 17, 18, 19 and 21, posterior area 7 (7p), several areas of the posterior part of the middle and posterior suprasylvian sulcus, the pulvinar complex and the superior colliculus. These results show that the 2-deoxyglucose technique is useful to investigate cognitive brain functions, and that different sets of cortical and subcortical regions are activated during two visual tasks with similar visual stimulation.