OBJECTIVES: The study has been performed to investigate the mortality within the first year after resection in patients with primary lung cancer, together with associated prognostic factors including gender, age, tumour stage, comorbidity, alcohol abuse, type of surgery and post-surgical complications. METHODS: All patients (n = 3363) from the nationwide Danish Lung Cancer Registry with first resection performed between 1 January 2007 and 31 December 2011 were analysed by Kaplan–Meier techniques and Cox-regression analysis concerning death within the first year after resection. Covariates included gender, age, comorbidity (Charlson comorbidity index), perioperative stage, type of resection, registered complications to surgery and alcohol abuse. RESULTS: The cumulative deaths after 30 days, 90 days, 180 days and 360 days were 72 (2.1%), 154 (4.6%), 239 (7.1%) and 478 (14.2%), respectively. Low stage, female gender, young age, no comorbidity, no postoperative complications, no alcohol abuse and lobectomy as type of resection were favourable for survival. CONCLUSIONS: Our results demonstrate that resection in primary lung cancer impacts mortality far beyond the initial 30 days after resection, which is conventionally considered a time window of relevance for the adverse outcome of surgery. Increased efforts should be made for optimizing the selection of patients suited for resection and for identifying patients at increased risk of death after resection. Furthermore, patients should be monitored more closely and more frequently, in particular those patients with high risk of death after resection. [ABSTRACT FROM AUTHOR]