PURPOSE: to characterize lips and tongue posture, tone and mobility of mouth breathing children. METHOD: the subjects of this study, conducted in São Paulo, SP, Brazil, were 40 mouth breathing children, 26 (65%) male and 14 (35%) female, aging between 7 and 10-year old. MBGR protocol was used to evaluate the aforementioned aspects. RESULTS: the following results were obtained for lip posture: semi-open lips (32.5%), alternating between open and closed lips (27.5%), open lip posture (22.5%) and closed lips (17.5%). With regards to the upper lip tone: 90% showed normal muscle tone, 10% lower tone, and no subjects showed a higher muscle tone. As for the tone of the lower lip, 80.0% of the children showed lower muscle tone, and 20.0% normal muscle tone. For the lips mobility variable, 100% had their mobility close to the best scores. Regarding tongue posture, 57.5% had a low-lying resting tongue posture, 32.5% did not allow for observation of this variable, and in 10.0% of the subjects the tongue was placed in an interdental resting posture. As for tongue muscle tone, 52.5% showed lowered tone, and 47.5% were considered normal. When assessing tongue mobility, 100% had mobility close to the best scores. CONCLUSION: characteristics of posture, tone and mobility of lips in this study's mouth breathing children were: semi-opened lip posture, upper lip with normal tone, lower lip with lowered tonicity and normal mobility. Regarding tongue characteristics: low-lying resting posture, lowered muscle tone and normal mobility.