The present paper contains an investigation, resulting in a methodology that allows through the use of computational vision techniques in images of the children´s faces in school ages, the extraction of group of particular characteristics in the mouth´s region, in order to find useful information about the labial incompetence identification. This methodology is exposed in three fundamental stages, selection of the mouth´s region of interesting, segmentation and parametrización of the lip´s extern and intern contours; and the proposal and computing of representative shape´s descriptors of lip´s morphology.