there are few systematic studies reporting the prevalence of oral mucosal lesions in children. The reported prevalence is ranging from 4.1 % to 52.6 %, probably due to differences in methodology and population. The aim was to identify the prevalence of oral mucosal lesions in children population.a cross, descriptive, retrospective study in children who attended the dental clinic San Lorenzo Atemoaya was done (January 2006-July 2009); the data was obtained from medical records. Oral mucosal lesions were recorded. Descriptive analysis and unconditional logistic regression were conducted.the sample was 367; there were 200 males (54.5 %). The median age was six years. The prevalence of oral mucosal lesions was 66.2 %. The most common lesions were cheilitis simple (41.1 %), melanotic macule (18.3 %), petechiae (16.9 %) and traumatic ulcer (12 %), without difference between sexes. The sucking lip was associated with cheilitis simple (OR 1.7, p = 0.013) and recurrent ulcers with onychophagia (OR 15.75, p = 0.026).it was observed a higher prevalence of oral mucosal lesions in children than reported in other papers. Association is confirmed between parafunctional habits and oral mucosal lesions.