Inhaled therapy is widely used for treatment of many respiratory disorders. Drug delivery in lungs is dependent on the correct use of aerosol devices and patients’ training is vital for a correct therapy administration. Therefore, is very important to assess the skills of professionals involved in training patients to the correct use of inhaler devices. The aim of this study was to check the practical skills and the theoretical knowledge of health care personnel in our University Hospital in using aerosol therapy and to determine differences among professional figures in the management of inhaler devices. Three hundred and fifteen (315) volunteers including physicians, residents, nurses and respiratory physiotherapists were enrolled; an independent professional, not working in our University Hospital, assessed their theoretical knowledge related to aerosol throughout a questionnaire. Practical skills were assessed through placebo simulation with the devices that participants declared to use frequently with patients. None of the respondents correctly answered all questions evaluating theoretical knowledge on the proper use of aerosol therapy. Respiratory physiotherapists obtained significantly better results with 17.2 (1.3) average points compared to 10.3 (3.7) obtained by doctors, 9.0 (3.0) by nurses and 9.1 (4.5) by residents. Analysing in detail physicians’ results, pneumologists showed better theoretical knowledge than other specialists. Concerning the practical skills, about 80% of those stating they knew how to use metered dose inhalers, made mistakes in the basic steps for proper inhalation technique and over 50% of respondents were unable to properly simulate placebo administration of dry powder inhalers. Also here, respiratory physiotherapists and pneumologists had significant better performances, when compared to other health professionals. Our data are in line with those published in the literature in other international clinical settings, noting inadequate practical and theoretical knowledge of the available devices for aerosol therapy.