In psychiatric patients the identification of cognitive deficits which predict a poor clinical outcome is important for the development of specific treatment strategies aimed at the amelioration of these impaired cognitive functions to increase the likelihood of full clinical remission. However, such attempts are absent in bulimia nervosa (BU), are scarce in anorexia nervosa (AN) and, furthermore, provide conflicting results. In the present prospective study we investigated the neuropsychological demands in 12 patients with AN and in 14 patients with BU before, during, and after a treatment period. At the initial testing session, both patients samples showed similar and impaired performance levels on tasks measuring attentional demands and problem solving abilities, while their mnemonic functions were preserved. At the final testing session, which took place 7 months thereafter, the impaired cognitive functions had improved to a similar degree in the AN and the BU subgroups. However, although the eating disorder symptomatology had ameliorated in parallel, no direct associations could be established with the initial neuropsychological demands and their rectification, respectively. On an individual level, 11 patients initially showed obvious cognitive deficits. However, the clinical characteristics of this subgroup differed not from that found in the 15 'good performers'. These findings indicate that the cognitive functions in the acute AN and BU are similarly impaired, but also ameliorate in a similar manner with clinical remission. Because no associations were obvious between cognitive and clinical rectifications, significant contributions of mediating factors (e.g., changes in metabolic brain turnover and in steroid hormones) are suggested.