ObjectivesLung cancer screening programmes offer an opportunity to address tobacco dependence in current smokers. The effectiveness of different approaches to smoking cessation in this context has not yet been established. We investigated if immediate smoking cessation support, including pharmacotherapy, offered as part of a lung cancer screening programme, increases quit rates compared to usual care (Very Brief Advice to quit and signposting to smoking cessation services).Materials and methodsWe conducted a single-blind randomised controlled trial of current smokers aged 55–75 years attending a Targeted Lung Health Check. On randomly allocated days smokers received either (1) immediate support from a trained smoking cessation counsellor with appropriate pharmacotherapy or (2) usual care. The primary outcome was self-reported quit rate at 3 months. We performed thematic analysis of participant interview responses.ResultsOf 412 people attending between January and March 2020, 115 (27.9%) were current smokers; 46% female, mean (SD) 62.4 (5.3) years. Follow-up data were available for 84 smokers. At 3 months, quit rates in the intervention group were higher 14/48 (29.2%) vs 4/36 (11%) (χ²3.98, p=0.04). Participant interviews revealed four smoking-cessation related themes: (1) stress and anxiety, (2) impact of the COVID-19 pandemic, (3) CT scans influencing desire to quit and (4) individual beliefs about stopping smoking.ConclusionThe provision of immediate smoking cessation support is associated with a substantial increase in quit rates at 3 months. Further research is needed to investigate longer-term outcomes and to refine future service delivery.Trial registration numberISRCTN12455871.