PURPOSE: to observe the lingual frenulum characteristics that may interfere with the functions of suction and deglutition in full-term infants in order to have a final version of the protocol designed by Martinelli et al (2012). METHOD: the lingual frenulum evaluation protocol was administered to a 100 healthy full-term infants. Two speech-language pathologists experienced in lingual frenulum evaluation analyzed the films taken during the evaluation. Chi-squared test, Fisher test and Analysis of Variance test were used considering qualitative and quantitative data respectively. RESULTS: 16 infants had lingual frenulum alteration. It was observed that there was a relationship between: a) tendency of tongue position during crying and time between feedings; b) the shape of the tongue when elevated and fatigue during feeding; c) lingual frenulum attachment to the tongue and the tongue movement during non-nutritive sucking. By analyzing the data of the infants with frenulum alteration it was possible to define the indicating characteristics of alteration. Those characteristics made the re-designing of the protocol and the scores attribution possible. CONCLUSIONS: the shape of the tongue when elevated during crying interferes with the tongue movement during the non-nutritive sucking. The place of frenulum attachment to the tongue interferes with the suction rhythm during breastfeeding. The new protocol with scores is considered to be an effective tool to assess and diagnose anatomical alterations of the lingual frenulum and its possible interference with breastfeeding.