For over a century, nebulizers have been commonly used to deliver aerosolized medications in the treatment of patients with pulmonary diseases. They are the aerosol device of choice when patients can not coordinate inhalation and actuation needed for the use of the pressurized metered-dose inhalers (pMDIs) or are not able to provide the necessary inspiratory flow required by the dry powder inhaler (DPI) for effective aerosol drug delivery. Three types of nebulizers exist: (1) jet nebulizers, (2) ultrasonic nebulizers, and (3) mesh nebulizers. The purpose of this paper is to explain the types of nebulizers available on the market and to evaluate their efficiencies in aerosol drug delivery while suggesting strategies for the optimal treatment of patients with pulmonary diseases.