Background: although concurrent chemoradiotherapy (cCRT) increases survival in patients with inoperable, locally advanced non-small-cell lung cancer (NSCLC), there is no consensus on the treatment of elderly patients. The aim of this study was to determine the prognostic value of the comprehensive geriatric assessment (CGA) and its ability to predict toxicity in this setting. Methods: we enrolled 85 consecutive elderly (⩾75 years) participants, who underwent CGA and the Vulnerable Elders Survey (VES-13). Those classified as fit and medium-fit by CGA were deemed candidates for cCRT (platinum-based chemotherapy concurrent with thoracic radiation therapy), while unfit patients received best supportive care. Results: fit (37%) and medium-fit (48%) patients had significantly longer median overall survival (mOS) (23.9 and 16.9 months, respectively) than unfit patients (15%) (9.3 months, log-rank P=0.01). In multivariate analysis, CGA groups and VES-13 were independent prognostic factors. Fit and medium-fit patients receiving cCRT (n=54) had mOS of 21.1 months (95% confidence interval: 16.2, 26.0). In those patients, higher VES-13 (⩾3) was associated with shorter mOS (16.33 vs 24.3 months, P=0.027) and higher risk of G3-4 toxicity (65 vs 32%, P=0.028). Conclusions: comprehensive geriatric assessment and VES-13 showed independent prognostic value. Comprehensive geriatric assessment may help to identify elderly patients fit enough to be treated with cCRT.