Objective Although there is no definitive consensus on the impairment of neuropsychological functions, most studies of adults with Anorexia Nervosa (AN) find impaired functioning in cognitive domains such as visual–spatial abilities. The objective of this study is to assess the cognitive functions in adolescents with AN before and after weight recovery and to explore the relationship between cognitive performance and menstruation. Methods Twenty-five female adolescents with AN were assessed by a neuropsychological battery while underweight and then following six months of treatment and weight recovery. Twenty-six healthy female subjects of a similar age were also evaluated at both time points. Results Underweight patients with AN showed worse cognitive performance than control subjects in immediate recall, organization and time taken to copy the Rey's Complex Figure Test (RCFT). After weight recovery, AN patients presented significant improvements in all tests, and differences between patients and controls disappeared. Patients with AN and persistence of amenorrhea at follow-up (n=8) performed worse on Block Design, delayed recall of Visual Reproduction and Stroop Test than patients with resumed menstruation (n=14) and the control group, though the two AN groups were similar in body mass index, age and psychopathological scale scores. Conclusion Weight recovery improves cognitive functioning in adolescents with AN. The normalization of neuropsychological performance is better in patients who have recovered at least one menstrual cycle. The normalization of hormonal function seems to be essential for the normalization of cognitive performance, even in adolescents with a very short recovery time.