Background & Objectives: Despite with low pancreatic cancer detection rate and low cost effectiveness, abdominal ultrasound (US) is recommended for detecting pancreatic cancer in Japan’s “Clinical Practice Guidelines for Pancreatic Cancer”, and main pancreatic duct (MPD) dilation is considered important for detecting pancreatic cancer. Here, factors related to MPD dilation were investigated. Methods: Of 124,454 participants who received consultation, BMI, blood pressure and blood tests, and US from 2012 to 2014, 3,357 were excluded for poor pancreatic imaging and 60,705 as duplicates, for a total of 60, 397 patients. For duplicate patients, data from the last examination was used. Using SPSS we performed a multivariate analysis separated by sex with smoking, age, drinking habits, BMI, hypertension, diabetes, and LDL-C as independent variables, and with MPD dilation (greater than 2mm). Smoking habits were categorized into nonsmokers, former smokers and smokers, and even further according to the Brinkman Index (BI) as < 400, 400-599, 600-799, and 800 <. Results: MPD dilation was found in 343 patients (0.57%). The multivariate analysis showed no association for male or female nonsmokers or smokers with BI < 400. In men, compared to nonsmokers, smokers (BI: 400-599, 600- 799, >800) were found to have a positive association respectively (OR: 2.83, 4.31, 1.99). In women, smokers (BI: 600-799) were found to have a positive association (OR: 7.23). Conclusion: We demonstrated a significant association between smoking habit and MPD dilation. Because MPD dilation may be associated with pancreatic cancer, even more thorough screening using US is necessary among smokers.