Some neuropsychological studies of anorexia nervosa (AN) have yielded conflicting results, and it has been established that not all adult patients with AN are cognitively impaired. The objective of this study is to determine the percentage of adolescents with AN who present worse cognitive functioning according to neuropsychological criteria of cognitive impairment, and to study their clinical characteristics. Thirty-seven adolescents (11-18 years) with a diagnosis of AN in an acute state of the illness and with low body mass index (BMI) were compared with 41 healthy subjects of the same sex and similar age and intelligence using a comprehensive neuropsychological battery. Overall, AN patients took longer to copy Rey's Figure than the control group (p = 0.001). Thirty per cent of patients showed impaired neuropsychological functioning (defined as scoring two standard deviations lower than the average or lower than their intelligence level in two tasks) with worse performance on visuo-spatial tasks. This subgroup of patients presented lower BMI (p = 0.023) and higher trait anxiety (p = 0.028). The performance of adolescents in an acute state of AN was similar to that of the healthy control group, with the exception of lower time to completion in copying a complex figure. However, cognitive performance varied in these patients, being clearly impaired in one-third of the sample. The cognitive impairment subgroup showed lower BMI and higher anxiety. Longitudinal follow-up studies are necessary to assess the stability of this profile after longer treatment periods.