abstract Background Obsessive Compulsive Disorder is considered to be a heterogeneous neuropsychiatric disorder with discrete symptom dimensions [1,2] and it has been proposed that there might be distinct neural systems related to the symptom dimensions. In this study, we examined the gray matter (GM) correlates of symptom dimensions in a large sample of DSM IV OCD patients in addition to comparing the GM volumes between OCD patients and healthy controls (HC). Method Voxel-based morphometry (VBM) analysis was performed on 3- T structural T1-weighted Magnetic Resonance Imaging (MRI) scans derived from participants recruited from a single center at the National Institute of Mental Health And Neurosciences (NIMHANS), India. The subjects were assessed using the Mini International Neuropsychiatric Interview (MINI), Yale Brown Obsessive Compulsive Scale (YBOCS) and the Dimensional YBOCS (to ascertain the severity score across each symptom dimension). Regional GM volumes were compared between 179 OCD patients (99 unmedicated) with 180 HC [age:29.4±7.1vs. 26.7±5.0;p Results The patients had significantly deficient GM volumes in the following regions compared to HC: left side- precentral gyrus, inferior frontal gyrus, middle temporal gyrus, anterior cingulate gyrus, medial frontal gyrus; right side- superior temporal gyrus, hippocampus and middle occipital gyrus. Among the OCD patients, scores on various symptom dimensions had distinct GM correlates: contamination dimension-left middle temporal gyrus and right inferior parietal lobule (negative correlation); pathological doubts- right middle frontal gyrus, left medial frontal gyrus, right superior frontal gyrus, left parahippocampal gyrus, left medial frontal gyrus, right superior temporal gyrus, right middle occipital gyrus, left superior temporal gyrus (positive correlation); sexual/blasphemous dimension-left inferior temporal gyrus, left cerebellum (positive correlation) and left precentral gyrus (negative correlation). Conclusions OCD patients had significantly deficient GM volume in widespread gray matter regions. The present study demonstrates in a large sample of OCD patients that there are symptom dimension specific GM correlates, supporting the premise that OCD is a neurobiologically heterogeneous disorder with discrete neural correlates across symptom dimensions.