Histopathological diagnosis of oral lichen planus is not easy since some cases of epithelial dysplasia may present traits which are very similar to those from lichen planus. Aim: to compare cell alterations which suggest malignancy present in oral lichen planus with those from epithelial dysplasia. Material and methods: histological cross-sections of oral lichen planus and dysplasia, dyed by hematoxylineosin, were analyzed by means of light microscopy. Results: variance analysis (alpha=5%) revealed a statistically significant difference between the average number of cell alterations in the lichen planus (5.83±1.61) and epithelial dysplasia (4.46±1.26). The chi-squared test did not show statistically significant differences between oral lichen planus and epithelial dysplasia in relation to the following cell alterations: increase in nucleus/cytoplasm ratio, nuclear hyperchromatism, irregular chromatin distribution and enlarged nuclei (p>0.05). Conclusion: Some cell alterations which suggest malignancy present in the oral lichen planus may also be found in epithelial dysplasia, impairing its diagnosis and, consequently, stressing the importance of following these patients in the long run. © Revista Brasileira de Otorrinolaringologia. All Rights reserved.