Objective: The objective of this study was to extend the Consequences of Screening (COS) Questionnaire for use in a lung cancer screening by testing for comprehension, content coverage, dimensionality, and reliability. Methods: In interviews, the suitability, content coverage, and relevance of the COS were tested on participants in a lung cancer screening program. The results were thematically analyzed to identify the key consequences of abnormal and false-positive screening results. Item Response Theory and Classical Test Theory were used to analyze data. Dimensionality, objectivity, and reliability were established by item analysis, examining the fit between item responses and Rasch models. Results: Eight themes specifically relevant for participants in lung cancer screening results were identified: "self-blame," "focus on symptoms," "stigmatization," "introvert," "harm of smoking," "impulsivity," "empathy," and "regretful of still smoking." Altogether, 26 new items for part I and 16 new items for part II were generated. These themes were confirmed to fit a partial-credit Rasch model measuring different constructs including several of the new items. Conclusion: In conclusion, the reliability and the dimensionality of a condition-specific measure with high content validity for persons having abnormal or false-positive lung cancer screening results have been demonstrated. This new questionnaire called Consequences of Screening in Lung Cancer (COS-LC) covers in two parts the psychosocial experience in lung cancer screening. Part I: "anxiety," "behavior," "dejection," "sleep," "self-blame," "focus on airway symptoms," "stigmatization," "introvert," and "harm of smoking." Part II: "calm/relax," "social network," "existential values," "impulsivity," "empathy," and "regretful of still smoking".