ABSTRACT: Lesions of the oral mucosa are a broad range of different alterations located in the soft tissue of the oral cavity. The studies that describe the prevalence of oral mucosal lesions have been carried out mainly in an adult population. Therefore, in the literature available both in Chile and abroad, there are few reports about pathological lesions and alterations of the normality of the oral mucosa in pediatric population. A descriptive observational cross-sectional study was conducted, with non-probability sampling for convenience, with a sample of 219 patients and a level of confidence of 95 %. We estimated 30 % of children with oral mucosal lesions. Patient history and the presence of oral mucosal lesions were registered in the clinical records specific to this study. In 101 patients a prevalence of 37.62 % of oral mucosal lesions was observed. The most frequent lesion was the minor aphthous ulcer (6.9 %), followed by irritation fibroma (5 %), traumatic ulcer (5 %), traumatic erosion (4 %), impetigo (4 %), pigmented lesion (3 %), and others, at lower rates. The most prevalent location was the lips with a 38.5 %.