INTRODUCTION: The aim of this study was to investigate possible effects of diabetes mellitus on clinical manifestations and prognosis of pancreatic cancer (PC). PATIENTS AND METHODS: We retrospectively reviewed the clinical files of 122 patients with PC, and divided them into two groups: those with diabetes (56 patients) and those without diabetes (66 patients). The two groups were then compared for demographic profiles, clinical manifestations of PC, features of the tumor and fatal outcomes. RESULTS: Mean age, sex distribution, body mass index at cancer diagnosis, prevalence of hypertension, dyslipidemia, weight loss, abdominal pain, lumbar pain, signs of dyspepsia, and size, and histological features of the tumor were similar between the two groups. The cancer was located in the head of the pancreas in 50% of those with diabetes, and 80% of those without diabetes (P=0.04). The median survival time was similar. CONCLUSIONS: Clinical features, tumor size and prognosis of PC are similar in people with and without diabetes. Having diabetes does not seem to contribute to earlier diagnosis of PC.