Few epidemiologic investigations of visceral adiposity and colorectal neoplasms have attempted the direct quantification of visceral fat. The authors measured visceral fat volume among middle-aged and elderly Japanese men and women who underwent colonoscopy and positron emission tomography/computed tomography for cancer screening in Tokyo, Japan, between February 2004 and February 2005, and examined the association between visceral adiposity and colorectal adenoma in 1,205 eligible subjects. Odds ratios and 95% confidence intervals for colorectal adenoma were estimated by using an unconditional logistic regression model after adjustment for potential confounders. Despite its high correlation with body mass index, visceral fat volume was associated with the prevalence of colorectal adenoma independently of body mass index in both sexes. After further adjustment for body mass index, the odds ratio of colorectal adenoma for the highest compared with the lowest quartile of visceral fat volume was 1.58 (95% confidence interval: 1.11, 2.24) for men and women combined. Conversely, body mass index was unlikely to modify the association between visceral fat volume and colorectal adenoma (P(interaction) = 0.39). These findings add to accumulating evidence that visceral adiposity exerts an important influence on the pathogenesis of colorectal neoplasms. The mechanisms of this potential association between visceral adiposity and colorectal carcinogenesis warrant further investigation.