We compared the particle size and fine particle fraction (FPF, % ≤5 μm) of 3 mesh nebulizers using cascade impaction with a Next Generation Impactor (NGI) and a modified laser diffraction method with a Spraytec particle sizer. Three of each nebulizer brand (InnoSpire Go [production equivalent], Aeroneb Go, and MicroAir U22) were tested with 1 mL of 5 mg/2.5 mL salbutamol sulphate in triplicate with a 15 L/min constant flow rate. NGI tests: the nebulizer was connected to the NGI and run until treatment completion; samples from the NGI were analyzed via high performance liquid chromatography. Spraytec tests: the Spraytec was set up with the inhalation cell fitted with the sheath flow collar with ports open, the flow straightener component fitted and connected to a vacuum pump such that there was 15 L/min flow at the inlet adapter ferrule. The nebulizer was connected to the inlet adapter ferrule; the nebulizer was run and stopped after 60 seconds of data measurements following a 10-second prime. The differences between the results of the NGI and Spraytec particle sizer were within 0.5 μm for particle size and 5% for FPF. The InnoSpire Go produced aerosols with the smallest particle sizes (mean ± standard deviation; 3.99 ± 0.26 μm MMAD and 4.17 ± 0.22 μm VMD) and largest FPFs (64.4 ± 4.42% and 63.4 ± 3.74%, respectively); the MicroAir U22 produced the largest particle sizes and smallest FPFs (5.83 ± 0.43 μm MMAD and 6.30 ± 0.19 μm VMD, and 41.3 ± 3.83% and 36.7 ± 1.62%, respectively). Span and geometric standard deviation were lowest for the InnoSpire Go. The modified Spraytec method has potential for use as a routine method in the future.