For a study, the researchers sought to measure and define the long-term effects of pneumonectomy, focusing on nononcologic mortality. Pneumonectomy was linked to significant alterations in cardiopulmonary physiology. Long-term results after pneumonectomy were usually measured in broad terms like disease-free and overall survival. Researchers looked at patients who had lobectomy or pneumonectomy for lung cancer at the facility between 2000 and 2018. For 12 clinicopathologic criteria, propensity-score matching was used. The complications and deaths after 90 days were compared. The 5-year cumulative incidence of oncologic and nononcologic death was compared using competing risks techniques. Researchers found 318 matched pairs out of 3339 lobectomies and 355 pneumonectomy patients. Overall complication rates were comparable after 90 days (46% for pneumonectomy vs 43% for lobectomy; P=0.40), but serious problems (21% vs 13%; P=0.005) and fatalities (6.9% vs 1.9%; P=0.002) were greater in the pneumonectomy group. There was no significant difference in the cumulative incidence of oncologic death between groups (P=0.9584). However, in both dates of surgery and 1-year landmark analyses, the cumulative incidence of nononcologic death was significantly greater in the pneumonectomy sample (P<0.0001 and P=0.0002, respectively). Nononcologic reasons killed 45 pneumonectomy patients (18%) 1–5 years after surgery; pneumonia (n=21) and myocardial infarction (n=10) were the most common causes. Preexisting cardiac comorbidity and a limited carbon monoxide diffusion capacity of the lungs were predictive of nononcologic mortality in pneumonectomy patients. Compared with lobectomy, excessive mortality after pneumonectomy lasted longer and was mostly due to nononcologic causes. Patients who have had a pneumonectomy require lifelong monitoring and may benefit from prompt evaluation and care at the first signs of sickness.