Research objectives: The objectives of this study were to examine the peculiarities of Oral lichen planus in patients of the Outpatient Clinic for Oral Medicine of the University Hospital Center of Split. We also aimed to investigate the incidence of other autoimmune diseases among patients diagnosed with OLP. Materials and methods: The data were collected retrospectively from the medical documentation of the Outpatient Clinic for Oral Medicine of the University Hospital Center Split. The study group included 64 subjects with OLP who were diagnosed through anamnesis and clinical examinationa as well as the representation of each clinical form and data. The disease was confirmed by histopathological analysis with the help of a biopsy. Anamnesis collected data on the subject's age and gender structure, the representation of each clinical form, and daily smoking and alcohol consumption habits. At the same time, data on the existence of another autoimmune disease in patients with OLP were collected. Results: Oral lichen Planus most often affected women (78.13%), middle-aged, and elderly (mean age 57.06 years). A higher incidence of OLP (81.25%) of erosive forms was recorded compared to non-erosive clinical forms. The majority of the test group were non-smokers (85.94%), and the majority of respondents (93.75%) did not consume alcohol on a daily basis. In addition to the diagnosis of OLP, a large percentage of subjects (70.31%) also had another autoimmune disease, among which the most common was Hashimoto's thyroiditis (20%). In the group of patients with other autoimmune diseases, the, most significant number of subjects (80%) had a diagnosis of another autoimmune disease before the diagnosis of OLP. In contrast, the most common autoimmune disease that was detected as part of the treatment due to oral manifestations was celiac disease, which was diagnosed in 2 patients (25%). Conclusions: Based on the results obtained, it can be concluded that oral lichen planus is a disease with is is an increased prevalence in middle-aged and older women, more frequent occurrence of erosive forms, and no direct link with the consumption of cigarettes and alcohol as etiological factors, which further confirmed the current findings. In patients diagnosed with OLP, the incidence of other autoimmune diseases is also increased.