Aerosol delivery to the lungs can be achieved with several devices that differ in their operating mechanisms and efficacies of aerosol delivery. There are several methods to measure aerosol delivery and deposition in a subject’s lung, in order to assess the efficacy of aerosol generators and the impact of certain drugs. Instruments such as cascade impactors, imaging techniques, and laser diffraction are available for measuring the particle size of aerosols, which is the main factor in the deposition and distribution of the produced aerosol. From impactors to laser diffractors, they have different operating mechanisms, analysis times, and characteristics, in which each has its own advantages and limitations. Several models are available to investigate aerosol delivery and deposition, such as in vitro, in vivo, and ex vivo models.