Aim: To investigate the prevalence of oral lichen planus in patients younger than 18 years, referred to a dermatology centre in Iran during 2002–2014. Lichen planus is a chronic inflammatory, immune-mediated disease that could affect the oral mucosa and is a pre-cancerous condition. The disease usually develops in middle age with female predominance and is rare in children. Methods: In this retrospective study, cases with definitive histopathologic diagnosis of lichen planus, over a 12-year period from 2002 to 2014 from a dermatologic hospital archive were evaluated. The prevalence of both cutaneous and oral lichen planus, the male:female ratio and site of involvement were calculated using SPSS version 21. Results: Thirty-six of 564 patients younger than 18 years old diagnosed with lichen planus. Two females (0.4%) had oral lichen planus. One patient had erosive, and one had bullous, oral lichen planus. Conclusion: Oral lichen planus had a very low frequency in Iranian population younger than 18 years old, identifying these patients is recommended for long-term follow-up.