OBJECTIVE: The study aimed to better understand the perceptions of mothers of preterm infants regarding smoking behaviors and environmental tobacco smoke (ETS) exposure using qualitative methodology.STUDY DESIGN: Using a Grounded Theory approach, we conducted in-depth, semi-structured interviews with mothers of preterm infants, both smokers and nonsmokers. Using the Theory of Planned Behavior (TPB) as a conceptual framework for our questions, we conducted and analyzed interviews until theoretical saturation was reached. Analysis included an iterative coding process resulting in theme development.RESULTS: Our key themes aligned with the TPB domains of attitudes, perceived control, and social norms. Regarding attitudes, mothers expressed that smoking was bad for their infants and that preterm infants were more vulnerable than term infants. Regarding perceived control, mothers commented on their perceived ability to avoid ETS exposure with subthemes including strategies utilized to mitigate ETS exposure risk. Some mothers expressed difficulty avoiding ETS exposure, for example, when residing in high-density housing. Regarding perceived social norms, mothers whose family and friends were nonsmokers expressed ease avoiding ETS, while mothers whose family and friends were smokers expressed more difficulty avoiding ETS.CONCLUSION: Mothers used a variety of behaviors within the domains of the TPB to reduce ETS exposures in their preterm infants which can inform future neonatal intensive care unit-based interventional strategies.KEY POINTS: · Mothers felt ETS is harmful for preterm infants.. · Mothers reported strategies for ETS avoidance.. · Mothers reported barriers to ETS avoidance.. · TPB can frame mothers' ETS-related behaviors..