The aim of this study was to determine prognostic factors for survival after resection of pancreatic adenocarcinoma (PC) and to compare outcomes after surgery alone versus surgery plus adjuvant therapy. We performed a retrospective review of 219 patients who underwent pancreaticoduodenectomy for PC with curative intent between 1995 and 2007. Data were collected prospectively. Postoperative adjuvant chemoradiation therapy (CRT) consisted of fluorouracil or gemcitabine-based chemotherapy; the median radiation dose was 45 Gy. The 3- and 5-year overall survival (OS) rates were 24.3% and 14.2%, respectively. Median OS was 14.0 months [95% confidence interval (CI), 12–16 months]. Patients with metastatic lymph nodes experienced improved median survival (16 vs 10 months; P < 0.001) and 3-year OS (3-year OS 28% vs 8%) after adjuvant CRT compared with those who had no CRT. Patients who underwent non-curative resection had the same effect (median OS, 13 vs 8 months; P = 0.037). Lymph node metastasis and non-curative resection showed no significance on multivariate analysis. Poor differentiation [risk ratio (RR) = 2.10; P < 0.001] and tumor size >3 cm (RR = 1.57; P = 0.018) were found to be adverse prognostic factors; adjuvant CRT had borderline significance (RR = 0.70; P = 0.087). Adjuvant CRT benefited a subset of patients with resected PC, particularly those with lymph node metastasis and those undergoing non-curative resection. Multivariate analysis demonstrated that patients with tumors larger than 3 cm and poor differentiation had poor prognosis.