Periodontitis is in an inflammatory process of the supporting tissue caused by specific microorganisms which leads to the progressive destruction of the periodontal ligament and alveolar bone. Respiratory disease, chronic obstructive pulmonary disease, is characterized by the combination of chronic bronchitis and emphysema with great pulmonal obstructions and inflammatory reactions, pneumonia characterized by the acute inflammation of the airways mostly by aspiration of S. pneumoniae, haemophilus, staphylococcus and others, and asthma characterized by chronic recurrent inflammatory episodes, hiperreactivity of the airways all with the allergic component, show a certain correlation with periodontitis and oral hygiene. Pneumonia has a more expressed correlation and the dentist has a role in reducing the number of dangerous pathogens, especially in the high-risk group of patients. Chronic obstructive pulmonary disease has some uncertain links with periodontitis, but still, it is proven that by improving the oral hygiene, one reduces the incidence of inflammatory exacerbations and improves the clinical status of the patient. Asthma correlates with periodontitis by aggravating its course and prognosis, enhances the incidence of caries, while reciprocally periodontitis can lead to asthma attack using various mechanisms and mediators on the pulmonal mucosal surface. Dentist’s role is to reduce the symptoms and the course of these systemic diseases reacting preventively and therapeutically on patient’s oral system.