High spatial resolution particulate matter measurements are necessary to accurately characterize urban air quality issues. This study investigates how sensors can be used in an urban area to complement existing air quality measurements. A measurement campaign was conducted during winter in Helsinki, Finland, where the performance of an optical Prototype Aerosol Sensor (PAS, (Shinyei PPD60PV and PPD42NS) and three commercial diffusion charging-based sensors (Pegasor AQ Urban, DiSCmini and Partector) were evaluated against reference instruments. The results showed that the PAS was able to measure coarse (PM2.5-10, range: 0–400 µg m-3) and fine (PM2.5, range: 0–50 µg m-3) fractions with reasonable correlation (R2 = 0.87 and 0.77) when compared to a gravimetric monitor. Likewise, the lung deposited surface area (LDSA) concentrations delivered by the three diffusion charging sensors indicated good performance (R2 range 0.97–0.92) when compared to LDSA concentrations calculated from the Differential Mobility Particle Sizer size distribution data. Clear correlation (R2 = 0.77) between the black carbon and the Pegasor LDSA as well as similar diurnal cycles were observed suggesting a common source. Optical sensors were found useful for measuring mass concentrations of local coarse particles. In contrast, diffusion charging sensors were found applicable in urban environments where traffic or other local combustion sources of ultrafine particles contribute to air quality.