Mois sans tabac (MST) is a social marketing operation, inspired by the British Stoptober. Organized every November in France since 2016, it aims to encourage smokers to stop smoking for 30 days. Smokers are invited to register on a website. Between 2016 and 2019, annual registrations ranged from 158290 to 243579. Since 2020, these figures have been steadily decreasing (112933 in 2021). The COVID-19 pandemic is part of the explanation in 2021, but the loss of momentum of MST leads to rethink the device.