Objectives:psychometric properties of the Turkish version of the Functional Assessment of Cancer Therapy-Lung (FACT-L) scale and the sensitivity tochanges in clinical indicators.Patients and Methods:This study was conducted within the framework of a national multicentre project. Patients with either stage IIIB or IV primary lungcancer diagnosed after April 2010were included in thisstudy. A classical confirmatory approach was used for both the reliability and validity analyses.Internal consistency was tested using Cronbach’s α value, and the validity analysis was performed using construct validity and clinical validity.Results:276 (92.3%) patients were male and the average age was 60.8 ± 9.4 years. The most frequently observed histological type was squamous cellcarcinoma (36.8%), and 61.5% of these stage IV tumours. Cronbachs α values for the subscales ranged from 0.60 to 0.84. The majority of the FACT-Lsubscales revealed inter-scale correlation coefficients greater than 0.35. All sub-dimensions, except that of the social/family well-being scale, are ableto significantly discriminate between stages IIIB and IV. Significantly lower scale scores were detected in patients with stage IV than stage IIIB. Thecomparative fit index was 0.917, and the root mean square error of approximation was 0.091. Dyspnoea, haemoptysis, chest pain, weight loss, anorexia,localised pain, and fever symptoms had a significant correlation with the FACT-L, trial outcome index, and lung cancer subscale.Conclusion:Turkish version of the psychometric properties of the original FACT-L scale is regarded as a valid and reliable tool and can be used safely ina clinical context when managing patients with lung cancer in Turkey.