Structural and functional brain abnormalities have been described in anorexia nervosa (AN). The objective of this study was to examine whether there is abnormal regional brain activation during a working memory task not associated with any emotional stimuli in adolescent patients with anorexia and to detect possible changes after weight recovery. Fourteen children and adolescents (age range 11-18 years) consecutively admitted with DSM-IV diagnosis of AN and fourteen control subjects of similar age were assessed by means of psychopathological scales and functional magnetic resonance imaging (fMRI) during a working memory task. After seven months of treatment and weight recovery, nine AN patients were reassessed. Before treatment, the AN group showed significantly higher activation than controls in temporal and parietal areas and especially in the temporal superior gyrus during performance of the cognitive task. Control subjects did not show greater activation than AN patients in any region. A negative correlation was found between brain activation and body mass index and a positive correlation between activation and depressive symptomatology. At follow-up after weight recovery, AN patients showed a decrease in brain activation in these areas and did not present differences with respect to controls. These results show that adolescent AN patients showed hyperactivation in the parietal and especially the temporal lobe during a working memory task, suggesting that they must make an additional effort to perform at normal levels. This activation correlated with clinical variables. In these young patients, differences with respect to controls disappeared after weight recovery. (Contains 2 figures and 3 tables.)