In Sweden the risk for female Anorexia Nervosa and Bulimia Nervosa is estimated to 1%. Females have ten times higher prevalence than males. Attention Deficit Hyperactivity disorder (ADHD) on the contrary has a male 2-3 times dominante. Among adults aprox. 3% has ADHD. ADHD is complex with at least one major associated psychiatric diagnosis. The aim of the present study was to investigate whether clinical findings, not just related to Eating Disorder (ED), could match ADHD as a co-existing diagnosis, as well as to follow the patients the first months after treatment with Methylfenidate had been induced. Five patients, one male and four females, age 18-43, with a history of Eating Disorder (ED) of 5-35 years, were clinically described with DSM-IV diagnoses, treatment regimen and therapeutic outcome. They suffered from disability in normal social functioning, i.e. education, professional career and family life. All of them had symptoms matching ADHD. In this case report the assumtion is made that treatment with Methylfenidate lead to an decrease of ADHD-symptoms as well as typical ED-symptoms, better social functioning and increased quality of life.