This study provides insights into the performance of a new nano-water-based condensation particle counter (N-WCPC, TSI 3788) and presents a comparison to the well-established butanolbased ultrafine CPC (UCPC, TSI 3776). The suitability of the N-WCPC to measure ambient airborne nanoparticles of various compositions has been assessed with an urban background aerosol in a light industrial area and provided comparable results (within 2%) to the 3776 at various particle number concentrations. The subsequent investigation using laboratory generated nearly monodisperse positively charged sucrose, sodium chloride, proteins, emery oil, and candle-generated particles in the diameter range of 2–53 nm showed material-dependent N-WCPC cut-off sizes between 2.2 and 17.2 nm at standard operating temperatures.