BACKGROUND: The txt2stop trial demonstrated that smoking-cessation support delivered by text message doubles biochemically verified abstinence at 6 months. There was no significant heterogeneity in any of the pre-specified subgroups. AIM: To explore participants' experiences of the txt2stop intervention via a qualitative study using telephone interviews. DESIGN AND SETTING: Qualitative telephone interviews in the community. METHOD: Thematic content analysis of 1283 feedback forms was conducted to develop a topic guide for 25 telephone interviews. Key themes were identified and described. Any differences in the experiences of those who did, and did not, successfully quit were specifically explored. RESULTS: Participants liked the fact that smoking-cessation support delivered by text message was convenient, easy to access, and chemical free. They reported that the intervention was a reminder that they were quitting and why, provided emotional support, was a reminder of the physical benefits of stopping smoking, and they saved messages so they could refer back to them. However, the intervention was not helpful for all. Receiving texts about smoking could also stimulate craving, and the timing, frequency, and duration of messages were not optimal for some participants. Those who did not quit reported that additional factors influenced them, such as periods of stress or social events, or reported that they had been unable to cope with the physical effects of withdrawal, and combining text-message support with medication could help with this. CONCLUSION: Although the intervention did stimulate craving in some participants at some times, recipients reported that it also provided emotional support and reinforcement at temporally appropriate moments. It was successful at helping people to quit smoking but could be used together with other forms of smoking-cessation support.