The fact that there are different epidemiological definitions of periodontitis and different evaluation protocols affects the estimate of periodontitis prevalence and of the influence of associated factors. The gold standard for periodontal examination is full-mouth record assessing CAL and PD. However, there are not always sufficient human and financial resources available to apply such assessment for epidemiological surveillance systems. Aim: This study was conducted to compare different protocols and definitions of periodontitis for assessing prevalence and the impact of related factors in adult patients who requested care at the School of Dentistry, UdelaR. Materials and Method: This was a cross-sectional study of 410 subjects with a high burden of disease in terms of NCDs and periodontitis. Clinical examination evaluated PD in all teeth and CAL in the CPI sextants (WHO 2013). Four periodontitis criteria were defined based on two examination protocols (WHO 2013 and WHO 1997) and two definitions of epidemiological case. Comparisons were made taking the 2013 WHO protocol as a reference. Results: Comparison of the two examination protocols showed that prevalence was underestimated when the WHO 1997 protocol was used to define moderate-severe and severe periodontitis, by 20% and 60%, respectively. Conclusions: When the severity of periodontitis was not considered, the WHO 2013 protocol did not provide more information on what factors increase the chance of periodontitis. However, when severity was considered, the associated factors were different. Consequently, in a small population, it would be worth using the WHO 2013 protocol, which is the closest to the full-mouth gold standard criterion. Keywords: cross-sectional studies - periodontal index - periodontitis - risk factors - non-communicable diseases