Objectives: In Japan, secondhand smoke (SHS) exposure in children has changed with increased heated tobacco products (HTPs) and electronic cigarettes (e-cigs) use. We clarified the status of home-based SHS exposure among children, including HTPs and e-cigs, as well as maternal perceptions on SHS avoidance and examined its association with health risks. Methods: This cross-sectional questionnaire-survey-based study included 379 mothers who were raising children aged