Objectives The cost-effectiveness of low-dose computed tomography (LDCT) screening for lung cancer is uncertain. This study estimated the health gains, costs (net health system, and including ‘unrelated’) and cost-effectiveness of biennial LDCT screening among 55–74 years olds with a smoking history of at least 30 pack years, and (if a former smoker) having quit within last 15 years, in New Zealand. Methods We used a macrosimulation stage shift model with New Zealand-specific lung cancer incidence rates and intervention parameters from the National Lung Screening Trial, a health system perspective, and a lifetime horizon for quality-adjusted life-years (QALYs) and costs discounted at 3% per annum. We also examined heterogeneity by gender, ethnicity (Māori (indigenous population) versus non-Māori), age and current versus ex-smoking status. Results and Conclusion We estimated 0.037 QALYs gained (95% uncertainty interval (UI) 0.024–0.053) per eligible participant, at a cost of US $3606 ($2689–4681). The overall incremental cost effectiveness ratio (ICER) was US $104,000 per QALY gained (95% UI US $59,000–US $175,000). The cost-effectiveness varied moderately by socio-demographics, with the ‘best’ICER being US $52,000 for 70–74 year old Māori females and the ‘worst’ICER being US $142,000 for 55–59 year old non-Māori females. The ICER varied little by current smoking status, due to higher competing mortality risk limiting QALY gains for current smokers. The two scenarios that lowered the ICER the most were increasing the screening uptake to 100%(ICER= US $50,000 per QALY), and improving the sensitivity (from 93.8%–98%) and specificity (from 73.4%–95%) of the screening test (ICER= US $42,000 per QALY). Based on a threshold of GDP per capita per QALY gained (ie US $30,000), LDCT screening for lung cancer is unlikely to be cost-effective in New Zealand for any sociodemographic group.