BACKGROUND: In a previous study, using computerized analysis of fine motor behaviour, seriously underweight anorexia nervosa patients in the early phase of treatment were found to have shorter reaction times, but not movement times, in experimental drawing and copying tasks. These differences persisted with weight restoration. SAMPLING AND METHODS: Using computerized analysis of writing and drawing behaviour during the performance of a Digit Symbol Substitution Test, 15 anorexia nervosa patients were compared with 15 normal controls, matched for age, sex and educational level. Patients were retested after weight restoration, as were controls after a similar interval. RESULTS: Patients turned out to be superior in the cognitive, but not in the motor aspects of the Digit Symbol Substitution Test. These differences persisted after weight restoration. A practice effect, due to repeated testing, was found in both groups, which turned out to be cognitive in nature. CONCLUSIONS: The findings show that this new technique can add to the interpretation of classic neuropsychological tests. The results are compatible with previous findings of intact or even superior functioning in anorexia nervosa patients on neuropsychological tasks requiring considerable cognitive effort.