Purpose: The aim of this retrospective investigation was to examine the occurrence of periodontal disease in patients referred to a specialist clinic for neurosurgery and to explore possible associations between common systemic disorders and periodontal disease in an adult population in Greece. Materials and Methods: The study sample consisted of 1,652 individuals, 760 males and 892 females, aged 40 to 68 years, with a mean age of 57.3 ± 4.7 years. Data were collected by means of an oral clinical examination and a selfadministered questionnaire. Statistical analysis of questionnaire items was performed by using a multiple linear regression analysis model in order to estimate correlations between systemic disorders as independent variables, and the relative frequency of periodontal pockets of 5 mm or more and the frequency of clinical attachment loss of 6 mm or more as dependent variables. Results: The relative frequencies of periodontal pockets >= 5.0 mm and clinical attachment loss >= 6.0 mm as expressed in terms of mean values were 76% and 70.2%, respectively, for individuals who suffer from cardiovascular disease and 62.3% and 52.9% respectively, for those who suffer from respiratory disease. The depth of periodontal pockets was significantly and positively correlated to the presence of respiratory diseases (P = 0.0001) and diabetes mellitus (P = 0.0001) after adjustment for age, gender and smoking, whereas clinical attachment loss was significantly and positively correlated to the presence of diabetes mellitus (P = 0.0001) and cardiovascular diseases (P = 0.037). Conclusion: Based on the clinical criteria for established periodontitis, the current study supports associations between periodontal disease and systemic disorders such as diabetes mellitus, cardiovascular and respiratory diseases. Keywords: cardiovascular diseases, diabetes mellitus, health questionnaire, periodontitis, systemic disorders