Background. Many cancer patients who are smokers when starting cancer therapy continue smoking despite evidence of tobacco smoking as a risk factor for poor treatment response and secondary primary cancers. Small samples and inconsistent results in previous studies warrant further research to identify predictors of being a continuous smoker during and after radiotherapy. Material and methods. In the clinical database of the Danish Head and Neck Cancer Group (DAHANCA), we identified 1455 patients diagnosed with laryngeal cancer between 2000 and 2010, who were all smokers at date of diagnosis and treated with primary radiotherapy. Information on the socio-economic characteristics of the study cohort was obtained from Statistics Denmark the year prior to diagnosis. Logistic regression analyses were applied. Results. In the cohort of laryngeal cancer patients smoking before starting radiotherapy, 50% still smoked one year after radiotherapy similar to the percentage of smokers during treatment. Being younger than 60 years (OR 1.39, 95% CI 1.00-1.91), commenced smoking before the age of 15 (OR 1.77, 95% CI 1.32-2.38), having a poor WHO Performance status (OR 3.09, 95% CI 1.71-5.61), low income (OR 2.21, 95% CI 1.23-3.98) and living alone (OR 1.56, 95% CI 1.13-2.14) were associated with increased risk of continuous smoking during treatment. Similar findings were found two months and one year after radiotherapy, however, no association with living alone (OR 1.08, 95% CI 0.73-1.59) at the one-year follow-up. Tumor stage and the average number of cigarettes smoked per day before radiotherapy were not associated with being a continuous smoker. Conclusion. Younger patients, who had an early smoking initiation, a poor performance status, low income and lived alone, were most likely to continue smoking. Continuous smoking was not related to the extent of disease.