Background:
More and more local governments implement smoke-free outdoor environments in an effort to decrease adolescent smoking and denormalize smoking behavior. Unfortunately, compliance of smokers with such environments is often lacking. To better understand smoker’s compliance, we reviewed the international literature.

Methods:
We performed a realist review. This exploratory approach synthesizes existing evidence into a program theory that links smokers’ compliance with outdoor smoke-free environments with specific mechanisms and outcomes. The search was conducted in PubMed, Web of Science, Embase, and PsycINFO for all published articles until September 2023. Twenty-five peer-reviewed Englishlanguage articles were included, describing both quantitative and qualitative studies. From these articles, evidence was extracted about contexts and mechanisms that influence the compliance of smokers.

Results:
The program theory showed that smokers’ compliance with smoke-free outdoor environments increases if they accept the policy, have sufficient knowledge of the policy, and when the policy affects their motivation to quit smoking. However, these mechanisms may be hindered by the feelings of smokers as they might find it hard to make a successful quit attempt, are addicted to smoking, see smoking as a legit coping mechanism, use smoking to deal with stressful situations, have limited confidence in the effectiveness and associated enforcement, feel resistance towards the policy, and don’t understand the policy. The context in which these environments are implemented, such as communication about the environment, the associated stop-smoking facilities, and the size of the environment, influences mechanisms and the desired compliance.

Conclusions:
Compliance of smokers with smoke-free outdoor environments can be influenced by their acceptance and knowledge of the policy, as well as their motivation to quit. When creating smoke-free public outdoor spaces., these mechanisms are important to consider so that policymakers are better prepared for smokers’ reactions. This will benefit compliance with smoke-free outdoor areas.