Objective This systematic review sought to analyze the reasons for the differences between mortality rates of oral and oropharyngeal squamous cell carcinomas among countries with a high incidence of these cancers. Study Design Data were collected by applying a search strategy to seven databases - MEDLINE/PubMed, Web of Science, Scopus, LILACS, and EMBASE, as well as Google Scholar and Open Grey of the grey literature. Results Of the 5,317 articles found, the systematic review included 62 - 39 in the higher mortality group, and 23 in the lower mortality group. Tumors in the higher mortality group appeared to be advanced in size and clinical staging, with patients exhibiting more harmful habits. By contrast, tumors in the lower mortality group appeared to be smaller in size and be more related to HPV infection. Conclusion Countries with a higher mortality of oral and oropharyngeal squamous cell carcinomas presented a lower human development index (HDI) when compared to countries with low mortality. This may explain the differences between size and clinical staging in diagnosis as well as the presence of harmful habits, since countries with low HDI tend to have difficulties in healthcare access. This systematic review sought to analyze the reasons for the differences between mortality rates of oral and oropharyngeal squamous cell carcinomas among countries with a high incidence of these cancers. Data were collected by applying a search strategy to seven databases - MEDLINE/PubMed, Web of Science, Scopus, LILACS, and EMBASE, as well as Google Scholar and Open Grey of the grey literature. Of the 5,317 articles found, the systematic review included 62 - 39 in the higher mortality group, and 23 in the lower mortality group. Tumors in the higher mortality group appeared to be advanced in size and clinical staging, with patients exhibiting more harmful habits. By contrast, tumors in the lower mortality group appeared to be smaller in size and be more related to HPV infection. Countries with a higher mortality of oral and oropharyngeal squamous cell carcinomas presented a lower human development index (HDI) when compared to countries with low mortality. This may explain the differences between size and clinical staging in diagnosis as well as the presence of harmful habits, since countries with low HDI tend to have difficulties in healthcare access.