Due to the rapid development of the nanotechnology industry in the last decade, nanoparticles (NPs) are omnipresent in our everyday life today. Many nanomaterials have been engineered for medical purposes. These purposes include therapy for pulmonary diseases. On other hand, people are endeavoring to develop nanomaterials for improvement or replacement of traditional therapies. On the other hand, nanoparticles, as foreign material in human bodies, are reported to have potential adverse effects on the lung, including oxidase stress, inflammation, fibrosis and genotoxicity. Further, these damages could induce pulmonary diseases and even injuries in other tissues. It seems that nanoparticles may exert two-sided effects. Toxic effects of nanomaterials should be considered when their use is developed for therapies. Hence this review will attempt to summarize the two-side roles of nanoparticles in both therapies for pulmonary diseases and initiation of lung diseases and even secondary diseases caused by lung injuries. Determinants of these effects such as physicochemical properties of nanoparticles will also be discussed.