The purpose of this study is to understand the effects of social media on the motivation of users to quit smoking. We used data from 3,596 users of an existing smoking cessation mobile application to perform a cluster randomized controlled trial over a period of two months. Our treatment was a social-enabled solution integrated in the existing application. Users could interact with each other by publishing posts and comments through an online community. We collected usage behavior of the application like number of sessions, average session duration, daily active users and calculated the 30-day retention rate to assess the motivation of people to quit smoking and their level of success at the end of the controlled experiment. We compared these metrics and processed them through statistical test (T-test, survival analysis via Kaplan-Meier estimate) to understand the impact of the social features. Our main results showed that users participating actively to the social platform have a better retention, than users exposed but inactive and unexposed users. A higher frequency of social exchanges also improved the retention. At the same time, there was no clear positive effect for users exposed to the social-enabled solution, who did not participate. The number of sessions and average session duration were less relevant than regularity of usage over time to increase the chances of success. We have seen the positive influence of social media on people’s motivation to quit smoking and on the abstinence rate after a few weeks, which is opening opportunity for further research on the topic.