<p>The current study investigated the impact of Body Mass Index (BMI) on particle deposition and dose received in the human respiratory tract for three groups of exposed subjects (adult males, adult females and 10-year-old children). A dosimetry model, the Exposure Dose Model 2 (ExDoM2) was modified to take into account the subject’s BMI. BMI affects physiological parameters which in turn affect the deposition fraction and dose of particles in the respiratory tract. This study used literature data to incorporate the impact of BMI to physiological parameters. BMI influences particle deposition differently across different age groups and particle sizes. Higher BMI leads to higher particle deposition in children for all particle sizes while in adults BMI can either increase or decrease particle deposition depending on the particle size. Regarding particle dose, both mass dose of PM₁₀ and number dose of ultrafine particles (UFPs) increased with increasing BMI due to the higher inhalation rates. These results highlight that obese subjects receive higher dose in the respiratory tract than health weight subjects. After particle clearance, the highest dose was observed in oesophagus with the dose increasing by 86.2% for children for a BMI increase by 15&#xa0;kg/m², whereas an increase of 47.9% for adult males and 46.7% for adult females was calculated for a BMI increase by 20&#xa0;kg/m². This finding suggests a higher percentage increase of the dose received by children compared to adults.</p> Graphical Abstract <p></p>