Psychiatric comorbidity is common in patients with eating disorders (ED), but prevalence estimates are heterogeneous, probably due to methodological differences between studies (population, diagnostic method, sampling procedure etc.) and a few studies include men. The aim of this study is to investigate psychiatric DSM-IV Axis I comorbidity in a large sample of adult patients, both males and females, with the whole spectrum of DSM-IV ED diagnoses. Initial presentation assessment data on 11,588 adult men and women presenting to specialist ED clinics in Sweden between 2008 and 2012 were extracted from a large clinical database. Diagnostics were based on semi-structured interviews (SCID-I) and the Structured Eating Disorder Interview (SEDI). Seventy-one percent of the patients with ED had at least one other Axis I disorder. The most common type of diagnosis was anxiety disorders (53%), where generalized anxiety disorder was the most common diagnosis. The highest levels of comorbidity were found for women with Binge Eating Disorder (BED) and men with Bulimia Nervosa (BN). Findings are consistent with previous research showing a high prevalence of psychiatric comorbidity in both men and women with ED. The small gender differences observed seem negligible compared to the general similarity in comorbidity.