ObjectiveTo investigate the expression of catechol O-methyltransferase (COMT) mRNA and its protein in colorectal adenoma tissues and corresponding adjacent tissues, colorectal cancer tissues and corresponding adjacent tissues. MethodsExpressions of COMT mRNA and its protein were evaluated by real-time PCR and immunohistochemistry method in colorectal adenoma tissues and corresponding adjacent tissues, colorectal cancer tissues and corresponding adjacent tissues. Meanwhile, the relationship between the expression of COMT and clinic-pathological features of colorectal adenoma and colorectal cancer were analyzed. Results①The expression of COMT mRNA in colorectal adenoma tissue/colorectal cancer tissue group was higher than that of corresponding adjacent tissue group (0.109 0 vs. 0.000 5, t=3.02, P=0.01; 0.041 8 vs. 0.013 5, t=2.71, P=0.02).②The rate of high-expression of COMT in colorectal adenoma tissue/colorectal cancer tissue group was higher than that of corresponding adjacent tissue group [72.34% (34/47) vs. 25.53% (12/47), χ2=28.72, P < 0.01; 66.67% (28/42) vs. 28.57% (12/42), χ2=4.97, P < 0.05].③High-expression of COMT was not related to age, gender, location of tumor, and pathological type in colorectal adenoma patients (P > 0.05). High-expression of COMT was not related to age, gender, location of tumor, and differentiation degree (P > 0.05), but was related to TNM staging, T staging, and N staging in colorectal cancer patients (P < 0.05), the patients of TNMⅠ+Ⅱstaging, T1+T2 staging, and N0 staging had higher rate of high-expression of COMT. ConclusionCompared with corresponding adjacent tissues, COMT expresses highly in colorectal adenoma tissues and colorectal cancer tissues, so it may play a partial role in the emergence and development of colorectal cancer.