Background: Dietary habits and smoking are recognised as important gastric cancer determinants. However, their impact on prognosis remains poorly understood. We aimed to quantify the association between lifestyles and survival of gastric cancer patients. Methods: In 2001–2006, 568 patients were recruited in the two major public hospitals in the north of Portugal. Participants were inquired about smoking and dietary habits regarding the year preceding the diagnosis. The vital status of all participants, up to 2011 (maximum follow-up: 10 years), was assessed through the North Region Cancer Registry. Cox proportional hazards regression models were used to estimate adjusted (at least for age, sex and education) hazard ratios (HR) and 95% confidence intervals (95% CI). Results: No significant differences in gastric cancer survival were observed according to smoking status (current vs never smokers, HR=1.00, 95% CI: 0.72–1.38) or alcohol intake (current vs never consumers, HR=0.87, 95% CI: 0.61–1.25). Only a dietary pattern (high consumptions of most food groups and low vegetable soup intake) was significantly associated with a better prognosis among patients with the extent of disease classified as regional spread (HR=0.45, 95% CI: 0.22–0.93). Conclusion: This study shows that prediagnosis lifestyles have a small impact in the survival of gastric cancer patients.