Oral cancer is a potentially fatal disease with an increasing incidence and an unchanged 5-year mortality rate. Unfortunately, oral cancer is often still late diagnosed, which leads to an increase in the likelihood of functional impairment due to treatment and mortality rate. Definitive diagnosis of oral cancer must be confirmed by scalpel biopsy and histological assessment. However despite its benefits, scalpel biopsy is invasive and it is burdened by a potential morbidity. Furthermore, previous studies have suggested a high degree of intraobserver and interobserver variability regarding the histological evaluation of malignancy. As a consequence, in recent years there has been a growing and persisting demand towards developing new non-invasive, practical diagnostic tools that might facilitate the early detection of oral cancer. The most investigated non-invasive adjunctive techniques are vital staining, autofluorescence, chemiluminescence, narrow band imaging, and exfoliative cytology. Aim of the review is to critically describe these adjunctive aids and, after considering the literature data, an expert opinion on the effectiveness and the possible use of each technique will be provided.