Abstract: In recent years, heated tobacco products (HTPs) have gained increasing popularity worldwide due to their reduced emissions of harmful substances compared to conventional cigarettes. To evaluate their environmental and health impacts, characterizing their physical and chemical properties is essential. This work employs a Scanning Mobility Particle Sizer (SMPS) to measure the puff-resolved concentrations of heated tobacco aerosols in real time. The aerosols were generated by two types of heating devices: an electromagnetic heating device and an infrared heating device. The puff-resolved concentrations of monodisperse particles at multiple selected sizes were measured to derive the overall size distributions. Subsequently, the puff-by-puff total particle number concentrations and mode diameters of the tobacco aerosols were determined. The key findings are as follows: (1) Due to distinct heating mechanisms, the aerosols produced by the two devices exhibit different puff-resolved distribution characteristics. The electromagnetic heating device offers relatively high heating efficiency but results in uneven heat distribution. Consequently, the aerosol concentration fluctuates within a range from 6.3 × 10⁶ to 8.9 × 10⁶ particles·cm⁻³, and the mode diameter varies between 220 and 283 nm. The infrared heating device provides more uniform heating but has lower heating efficiency, leading to a gradually increasing operating temperature during puffing, especially under insufficient preheating. The aerosol concentration increases puff-by-puff from 2.3 × 10⁶ to 8.7 × 10⁶ particles·cm⁻³, with mode diameters increasing from 151 to 319 nm. (2) Heated tobacco aerosol particles in different size ranges exhibit a distinct dependence on heating temperature. Smaller particles (≤ 80 nm) tend to be produced in large quantities at lower temperatures, while larger particles (≥ 300 nm) are more likely to be generated at higher temperatures. (3) The total particle concentrations and mode diameters of heated tobacco aerosols vary synchronously. The temperature of the heating device significantly affects both the total particle concentration and the mode diameter. As the heating temperature increases, both the aerosol concentration and the mode diameter rise markedly. These results demonstrate that the total particle number concentrations and mode diameters of heated tobacco aerosols are highly sensitive to the operating temperature and heating mechanism. Thus, the substantial release of small particles under insufficient heating conditions poses challenges for the design of heating control modules, emphasizing the need for adequate preheating and stable operating temperatures.