Pulmonary drug delivery refers to all the techniques used to deliver drugs and aerosols to the respiratory epithelium and epithelial cells directly through inhalation. It is used as a targeted therapy for the treatment of respiratory diseases such as chronic obstructive pulmonary disease, asthma and lung cancer. Drug delivery through the pulmonary route offers the distinct advantages of high bioavailability and no first-pass effect, which makes it an important means of delivering therapeutics directly to lung lesions. The benefits of pulmonary delivery include increased efficiency, a faster onset of delivery, decreased side effects, self-administration of non-invasive delivery, and localized action. The inherent properties of lungs such as their low enzymatic environment and high surface area make pulmonary delivery even more effective. This book provides significant information to help develop a good understanding of pulmonary physiology and drug delivery in respiratory diseases. Its extensive content will provide the readers with a thorough understanding of the subject.