In order to assess what the risk factors for patients with pancreatic cancer (PC) in Taiwan are, a retrospective study was undertaken among 282 consecutively enrolled inpatients with confirmed pancreatic cancer within the past 5 years. For comparison, 282 age- and sex-matched controls were consecutively enrolled. A history of smoking, consumption of alcohol, diabetes mellitus, cholecystectomy and gastric surgery were thoroughly reviewed. Smoking and diabetes mellitus were very common among patients with pancreatic cancer compared with controls (P < 0.01). A significant linear trend towards an increased odds ratios (OR) for the development of PC with a higher level of smoking was seen (P < 0.001). Diabetes mellitus (DM) also exhibited an increased risk (OR: 2.84; P < 0.01), while the risk still existed among those patients who had a diabetic history of more than 3 years. Among 129 histologically established PC patients, smoking remained as a risk factor for PC, while the linear trend with an increasing OR with increasing levels of smoking was confirmed again (P < 0.01). DM, particularly over the long-term, was also a risk factor for those histologically established PC patients. In summary, cigarette smoking and existing diabetes mellitus are probable risk factors for the development of pancreatic cancer in Taiwan.