Objectives: The purpose of this study was to investigate the prognostic impact of tumor volume (TV) on patients with stage I non-small cell lung cancer (NSCLC) after complete resection. Materials and Methods: We retrospectively reviewed the clinicopathological characteristics of 274 patients with stage I NSCLC who had received preoperative chest computed tomography (CT) scans and complete resection. TV was semi-automatically measured from chest CT scans by using an imaging software program. The optimal cutoff values of TV were determined by X-tile software. Disease-free survival (DFS) and overall survival (OS) were compared using Kaplan-Meier analysis. Univariate and multivariate analyses were performed to identify risk factors for DFS and OS. Results: By using 3.046 cm(3) and 8.078 cm(3) as two optimal cutoff values of TV, the patients were separated into three groups. The 5-year DFS and OS for patients with TV <= 3.046 cm(3), 3.046-8.078 cm(3), and > 8.078 cm(3) were 88.0%, 73.6%, and 62.1%, respectively (P < 0.001), and 91.4%, 84.5%, and 73.3%, respectively (p < 0.001). Multivariate analysis showed that age and TV were independent factors associated with DFS. Sex, age, histology, visceral pleural invasion, and TV were independent factors associated with OS. Stage Ia patients might be separated into three groups on the basis of TV with significantly different DFS and OS. Patients with tumor diameter <= 2 cm and 2-3 cm were also stratified into two groups with significantly different DFS and OS on the basis of TV, respectively. Conclusion: TV is an independent risk factor for DFS and OS for stage I NSCLC after complete resection. TV might provide additional prognostic information over tumor diameter in patients with stage I NSCLC. (C) 2016 Elsevier Ireland Ltd. All rights reserved.