OBJECTIVES: The Consequence of Screening in Breast Cancer questionnaire (COS-BC) assesses the psychosocial consequences of abnormal and false-positive screening mammography. It has two parts; one covering the period between abnormal screening and final diagnosis and one relating to the period following being declared free from cancer. The first aim of the study was to assess if COS (i.e. COS-BC without the breast specific items) was relevant for persons having false-positive lung cancer screening results. The second was to develop new items specifically relevant to participants in lung cancer screening. METHODS: A randomised study of lung cancer screening was launched in Denmark in 2005. Five focus groups were held with 20 people (13 women and 7 men; mean age 60.0 years) who had received an abnormal screening result in the prevalence round and were recalled for a scan after 3 months. They discussed their thoughts and feelings after being recalled and after receiving the final false-positive diagnosis. They completed the COS and discussed its relevance to their own experiences. The face and content validity of new items developed after the focus groups was tested by means of interviews with 6 participants from the focus groups RESULTS: The items in the COS were all relevant for lung cancer screening. Three themes were extracted from the audio-taped interviews. Stigmatisation, Self-blame and Focus on symptoms. Twenty-six new items for part I and 16 for part II of the questionnaire (COS-LC) were generated. CONCLUSION: There are many common psychosocial consequences of abnormal and false-positive screening in breast cancer and lung cancer. However, several new lung-specific items were needed to obtain high content coverage and, consequently, make the COS-LC relevant to lung cancer screening. The questionnaire is currently in use in the Danish randomised study and will be validated using Item Response Theory (the Rasch model).