Objectives: The aim of this specialist work was to identify and describe the important factors of improper drug administration by inhalation into the lungs resulting in unfavorable outcome of treating lung diseases and insufficient control of such diseases. In accordance with such factors, principles of guideline development for the proper use of the drug inhaled into the lungs, shall be established. The role of pharmacists in improving patient compliance and improve treatment outcomes, will be particularly emphasized. Material and methods: As a basis for writing this theoretical work, I was using scientific articles that provide an overview of the pathology of asthma and COPD, as well as existing inhalation devices, and an overview of the problem of good compliance and proper application of the drug inhaled into the lungs. Results: Successful drug administration into the lungs by inhalation depends on physical and chemical properties of the active substance and pharmaceutical form of the drug, on medical device which allows release of the prescribed dose and on administration by the patient (handling of the medical device and the force of inhalation). Given the current inhalers on the market, the pharmaceutical industry should focus their attentionon the development of inhalation devices for different patient populations, taking into account their age and health state in order to achieve the concept of "individualized inhaler". Conclusion: Drugs that are administered by inhalation into the lung are the basis of treatment of chronic lung disease and inhalers are the most commonly used devices for effective implementation. The pharmacist, because of its availability, is often in a position to provide expert advice on the proper application of drugs by inhalation into the lungs, and to participate in the development and improvement of guidelines for their proper implementation. Future guidelines for the proper use of the drugs by inhalation into the lungs should be based at least on the following principles: continuous assessment and improvement of the competence of health professionals, particularly pharmacists, in the field of the correct administration of the drug inhaled into the lungs; further improvement of device features through cooperation of all participants of the health care system while taking into consideration the knowledge and competence level of patients with the aim of developing and manufacturing devices that are easy to use; demonstration of the correct administration of the drug inhaled into the lungs using the inhaler by pharmacists; monitoring of treatment outcomes in interaction with a continuous assessment of the essential factors of proper administration of the drug inhaled into the lungs; public healthcare actions guided by the pharmacists to increase awareness of the importance for proper inhalation technique; development of universal inhaler for all drugs that are applied by inhalation into the lungs.