Objective: The purpose of this study was to compare published Oral Lichen Planus (OLP) diagnostic criteria. Study Design: After obtaining IRB approval, electronic health records at a tertiary care academic medical center from 2015 to 2021 were reviewed. Adult patients with OLP (ICD-10 code L43 and its subcategories) were included. Cases were excluded if histological analysis or outcomes were not reported. Results: 341 charts were reviewed. Patient mean age was 66.2±11.7 years and 74.4% were female. 79.7% had OLP lesions in multiple anatomical locations within the oral cavity. 90.3% had bilateral involvement. Skin and genital lesions were reported as 15.5% and 13.7% respectively. 86.5% of cases had plaque, reticular or Wickham striae (WS), whereas 17.8% had atrophy, erosion, or ulceration. When applying the available diagnostic criteria to this cohort, 100% of cases agreed with 1978 WHO criteria, 60.9% with 2003 modified WHO, 74.5% with 2016 AAOMP, and 70.4% with 2020 WHO. Clinicopathologic features agreed with all 4 published criteria in 60.9% of cases. Conclusions: The 1978 WHO criteria may lack specificity, while 2003 WHO could be too specific clinically and histologically. The 2016 AAOMP criteria may be too strict histologically, while the 2020 WHO criteria may be too strict clinically. Further prospective studies are needed to reconcile diagnostic criteria.