Comorbid depression is frequent in obsessive-compulsive disorder (OCD) and is acknowledged as a major confound in biological and neurocognitive investigations in OCD. The aim of the present study was to assess the distribution of depressive symptoms in a large OCD sample (n=162) and to analyze the dimensional structure of the Hamilton Depression Rating Scale (HDRS) in OCD. Major depressive disorder according to DSM-IV criteria was apparent in approximately one third of the patients. Frequent symptoms were depressed mood, reduced ability to work, anxiety symptoms and guilt feelings. HDRS scores were submitted to a varimax-rotated factor analysis. In accordance with studies conducted with depressed samples, multi-dimensional solutions suggesting three to six factors emerged. Subsequent confirmatory factor analysis revealed satisfactory fit indices for a four-factorial solution comprising core depressive symptoms, sleep disturbance, anxiety and gastrointestinal problems. Aggression-related obsessions as well as the overall severity of obsessions were related to core depressive symptoms. Anxiety symptoms were associated with excessive rituals. Greater recognition of depressive sub-components may help to raise the replicability of empirical findings in OCD research as there is evidence from both depression and OCD samples that distinct depressive syndromes have different biological correlates.