A qualitative short-term longitudinal study based on one-to-one semistructured interviews with users allocated to one of the 2 selected apps was conducted. The literature investigating the use of CBT in smoking cessation, specifically via a mobile digital platform, is limited. Due to this, an exploratory approach was used, setting out to gather data around the topic, the analysis of which would facilitate the emergence of research questions and theory. Thus, a qualitative, inductive approach was adopted. From the primary data collected, thematic analysis was carried out using a 6-phase framework . This was used to generate themes from ideas that emerged during the interviews. Descriptive statistics based on quantitative data gathered as part of the interviews are also provided.