Background <p>Particulate emissions from tobacco products vary significantly between product types. Understanding the nature and quantity of these emissions is important for health risk assessments. This study investigates the mainstream particulate matter emissions from tobacco products, comparing conventional cigarettes (CCs) and heated tobacco products (HTPs).</p> Objective <p>To characterise and compare the nature of aerosols emitted by CCs and HTPs in real time and online.</p> Methods <p>A volatile particle removal system, combining a thermo-dilution setup with an advanced catalytic stripper, was employed to separate and analyse total particulate emissions (including both solid and liquid phases) and the solid-only fraction. Particle number and mass concentrations, size distributions, and physical states of the emitted particulate matter were evaluated.</p> Results <p>The results demonstrate that HTPs emit considerably fewer particles than CCs, with HTP aerosols comprising liquid droplets, whereas CC smoke consists of both liquid and solid particles.</p> Conclusions <p>The findings provide critical insights into the composition and physical form of tobacco emissions, contributing to a better understanding of the differences between CC smoke and HTP aerosols and their potential health impacts.</p> Graphical Abstract <p></p>