Background: Colorectal surgical procedures have a high rate of surgical site infection (SSI), and obesity has been implicated as a predictor of such infection. We hypothesized that abdominal wall thickness (AWT), as a metric of obesity, would predict postoperative superficial and deep incisional SSI after colorectal surgery, and conducted a study to assess superficial and deep incisional SSI and its relationship to abdominal wall thickness. Methods: To measure pre-operative AWT through cross-sectional imaging, and to analyze its relationship to SSI, we conducted a retrospective study at a single academic medical center of patients who had had colorectal resection for any indication in 2008 and 2009. Results: We identified 143 patients for inclusion in the study. Superficial or deep incisional SSI occurred in 43 patients (30%). Abdominal wall thickness at the midpoint between the umbilicus and pubis was associated with SSI (OR 1.03; p=0.014). Body-mass index (BMI) was also significantly associated with SSI (OR 1.08; p=0.014). Other significant (p<0.05) predictors of SSI by univariate analysis included a history of soft tissue infection, a surgical wound classification of 3 or 4, and lack of compliance with perioperative antibiotic guidelines. In a multivariable analysis of factors that were statistically significantly associated with SSI in univariate comparisons, lack of appropriate preoperative antibiotic administration independently predicted SSI (OR 4.33; 95% CI 1.08-17.40), but AWT and BMI were not significantly associated with SSI. Conclusions: Surgical site infection is common after colorectal surgery. Increased AWT predicts SSI by univariate analysis. Our findings could guide further studies of interventions that may decrease the risk of SSIs in patients with a thick abdominal wall.