BACKGROUND: Due to the COVID-19 pandemic, from April 2020 data collection for the Smoking and Alcohol Toolkit Study (STS/ATS) shifted from a face-to-face to a telephone survey. In March 2022 a parallel face-to-face survey was conducted alongside the telephone survey to explore whether the change in data collection to telephone affected key sociodemographic, smoking alcohol use indicators. METHODS: Cross-sectional representative surveys (one telephone and one face-to-face) of adults aged 16+ in Great Britain. We estimated unweighted statistics and 95% confidence intervals for sociodemographic date. We estimated weighted prevalence statistics and 95% confidence intervals for selected smoking and alcohol use measures for Great Britain, England, Scotland and Wales separately, except nicotine product use, which was assessed for the overall Great Britain sample only. RESULTS: In March 2022, 2,607 and 2,064 adults aged 16+ participated in respective telephone and face-to-face surveys for the STS/ATS. The unweighted age profile of the face-to-face wave was younger than the telephone wave but similar according to other sociodemographic variables. Weighted estimates in the telephone and face-to-face surveys differed by around one percentage point or less for response categories of daily smoker, non-daily smoker, pipe/cigar smoker, and stopped last year. There were differences in the estimates for never smoking and stopped more than a year ago between the surveys but the combined estimate for never or long-term ex-smoking was similar. Data on use of nicotine products by past-year smokers were similar between survey modalities. The estimates for people reporting an AUDIT score of 8 or higher, or an AUDIT-C score of 5 or higher, and attempting to cut down on drinking were similar between modalities. A higher proportion of respondents reported never drinking during the past year in the face-to-face survey compared with the telephone survey. CONCLUSION: A parallel telephone and face-to-face survey wave of the STS/ATS yielded similar estimates for key sociodemographic, smoking and alcohol use measures. Differences between estimates are generally within expected limits given the uncertainty of month-to-month surveys.