Background: Lung cancer has a high impact on both patients and relatives due to the high disease burden and short life expectancy. Previous studies looked into treatment goals patients have before starting a systemic treatment. However, studies on relatives' perceptions of treatment at the end of life are scarce. Therefore, we studied the perspectives of relatives in hindsight on the achievement of treatment goals and the choice to start treatment for metastatic lung cancer of their loved one. Methods: We conducted a structured telephone interview study in six hospitals across the Netherlands, one academic and five non-academic hospitals, between February 2017 and November 2019. We included 118 relatives of deceased patients diagnosed with metastatic lung cancer who started a systemic treatment as part of usual care (chemotherapy, immunotherapy or targeted therapy with tyrosine kinase inhibitors (TKIs) and who completed a questionnaire on their treatment goals before the start of treatment and when treatment was finished. We asked the relatives about the achievement of patients' treatment goals and relatives' satisfaction with the choice to start treatment. This study is part of a larger study in which 266 patients with metastatic lung cancer participated who started a systemic treatment and reported their treatment goals before start of the treatment and the achievement of these goals after the treatment. Results: Relatives reported the goals 'quality of life', 'decrease tumour size' and 'life prolongation' as achieved in 21, 37 and 41% respectively. The majority of the relatives (78%) were satisfied with the choice to start a treatment and even when none of the goals were achieved, 70% of the relatives were satisfied. About 50% of relatives who were satisfied with the patients' choice mentioned negative aspects of the treatment choice, such as the treatment did not work, there were side effects or it would not have been the relatives' choice. Whereas, 80% of relatives who were not satisfied mentioned negative aspects of the treatment choice. The most mentioned positive aspects were that they tried everything and that it was the patient's choice. Conclusion: The majority of relatives reported patients' treatment goals as not achieved. However, relatives were predominantly satisfied about the treatment choice. Satisfaction does not provide a full picture of the experience with the treatment decision considering that the majority of relatives mentioned (also) negative aspects of this decision. At the time of making the treatment decision it is important to manage expectations about the chance of success and the possible side effects of the treatment.