The objective of this study was to compare body size estimation based on memory versus perception, in patients with anorexia nervosa (AN) and healthy controls, adjusting for possible confounders. Seventy-one women (AN: 37, controls: 35), aged 14–29 years, were assessed with a computerized body size estimation morphing program. Information was gathered on depression, anxiety, time since last meal, weight and height. Results showed that patients overestimated their body size significantly more than controls, both in the memory and perception condition. Further, patients overestimated their body size significantly more when estimation was based on perception than memory. When controlling for anxiety, the difference between patients and controls no longer reached significance. None of the other confounders contributed significantly to the model. The results suggest that anxiety plays a role in overestimation of body size in AN. This finding might inform treatment, suggesting that more focus should be aimed at the underlying anxiety. Copyright © 2014 John Wiley & Sons, Ltd and Eating Disorders Association.