Background In spite of all the efforts, recurrent aphthous stomatitis (RAS) and oral lichen planus (OLP) still have unexplained etiology. The role of anxiety, depression, and psychological stress in occurrence and intensity of symptoms in RAS and OLP patients has been investigated in this study. Methods A total of 110 patients with RAS in the acute phase and 112 patients with OLP also in acute phase participated in this study. All patients filled out questionnaires related to the primary disease (RAS/OLP) after which they took the following psychological tests: Beck Depression Inventory (BDI), The State‐Trait Anxiety Inventory (STAI), and Ways of Coping Questionnaire (WCQ). Results According to multiple regression analysis, in patients with RAS, the highest correlation was found between results of the pain intensity and STAI test (β= 0.66; p < 0.000). In the patients with OLP, the highest correlation was found between the level of hyperkeratosis and WCQ test (β = 0.53; P < 0.000), inflammation and results of BDI test (β = 0.33; P < 0.002), and results of dynia test and STAI test (β = 0.31; P < 0.004). Conclusions In this study, a high correlation between anxiety, depression, and psychological stress with symptoms of RAS and OLP has been observed.