OBJECTIVE Gemcitabine-based chemotherapy has been used as a standard treatment in patients with unresectable pancreatic cancer. However, the clinical outcomes of this regimen are still unsatisfactory in prolonging survival. We retrospectively analyzed clinical characteristics of patients with advanced pancreatic cancers who received gemcitabine-based chemotherapy and showed long-term survival. METHODS We enrolled 49 patients who underwent treatment with more than three cycles of gemcitabine-based chemotherapy. Long-term survivor was defined as patient who has survived more than 12 months after diagnosis. The clinical characteristics were analyzed to compare the differences between long-term and short-term survivors. Univariate or multivariate analyses were performed to identify prognostic factors associated with chemo-responses. RESULTS Twenty patients (41%) survived more than 12 months. Long-term survivors had smaller tumor size (OR 2.190, p=0.049, 95% CI 1.005-4.773) and higher serum BUN level (OR 0.833, p=0.039, 95% CI 0.701-0.990) compared to short-term survivors. Overall median and progression-free survivals were 11 and 4 months, respectively. Presence of distant metastasis (hazard ratio 1.441, p=0.035, 95% CI 1.002-2.908) was a significant independent predictor of progression-free survival. Tumor size (hazard ratio 1.534, p=0.004, 95% CI 1.150-2.045) was associated with overall survival. CONCLUSIONS Gemcitabine chemotherapy may be more effective and allow longer survivals in patients with clinical characters of smaller tumor size and normal serum BUN level at diagnosis. We suggest a well-designed large controlled study to evaluate the prognostic factors such as clinical characteristics and molecular biological features in patients with advanced pancreatic cancers who receive gemcitabine-based chemotherapy.