Background/Aims: The aims of this study were to determine the feasibility of diffusion-weighted imaging (DWI) for detecting bowel inflammation and to investigate the changes in the apparent diffusion coefficient (ADC) values in the inflamed bowel of patients with ulcerative colitis (UC). Methodology: Seven patients, who underwent DWI for UC and curative total colectomy because of insistence on conservative therapy, were enrolled in this study. The resected specimens were examined histopathologically to determine the degree of inflammation and the presence of malignancy. The ADC values of the lesions were calculated and compared among UC lesions. Results: The mean ADC value of the active UC lesions was significantly (p<0.01) lower than that of the normal colorectal tissue (1.12 +/- 0.14x10(-3) mm(2)/s vs. 1.60 +/- 0.21 x 10(-3)mm(2)/s, respectively). The mean ADC value of the active lesions was significantly (p<0.01) lower than that that of the healing lesions (1.12 +/- 0.14 x 10(-3) mm(2)/s vs. 1.62 +/- 0.28 x 10(-3)mm(2)/s, respectively). Conclusions: DWI may be valuable for following patients with UC, and the stage of UC may be diagnosed easily based on the ADC values.