Background: Obesity is an important risk factor for colorectal cancer (CRC); however, the exact role of adiposity on CRC remains unknown. Our overarching hypothesis is that abdominal fat, specifically visceral fat, through alterations in pro-inflammatory and tumor-promoting factors (e.g., IGF-1 or insulin) promotes aggressive tumor behavior and proliferation. To address this hypothesis, we have established an ongoing cohort of CRC patients [Colorectal Outcomes, Prognosis and Epidemiology (COPE) Study] with repeated adiposity and blood measures during the first year post-diagnosis. The objective of this study is to begin examining differences in diagnostic overall and abdominal adiposity by clinicopathological factors. Methods: Newly diagnosed patients with invasive adenocarcinoma of the colon or rectum were enrolled from 2010 to 2013 (N=213). Baseline overall adiposity by body mass index (BMI) and abdominal adiposity by waist circumference (WC) were collected. In a pilot study in 30 cases, baseline levels of IGF, IGFBP3, insulin and glucose to examine if serum markers were associated with obesity among CRC patients. The differences were evaluated by gender and clinical factors using ANOVA. Results: This study included 126 male and 87 female CRC patients with a median age of 64 years (range: 29-93). A majority of the patients were Caucasian (94%), married (68%), and never smokers (59%). The mean BMI and WC were 27.6±5.2 kg/m²and 96.5±15.8 cm, respectively. WC, but not BMI, was significantly higher among men (p=0.02), among patients with colon cancer (p=0.01), with higher stage (stage I/II vs. III/IV; p=0.02) and in high grade tumors (p=0.03). Serum IGFBP3 was significantly elevated in patients with abdominal adiposity (p=0.004) and colon cancer (p=0.004). Conclusions: Excess abdominal adiposity (WC) was related to advanced stage and high grade, whereas overall adiposity (BMI) was not. This study highlights the prevalence of abdominal adiposity and its potential biological importance among CRC patients. The development of more refined techniques (e.g. CT-based) of further defining the visceral and subcutaneous components of abdominal adiposity in cancer patients may prove to be informative.