Objectives:  To provide diagnostic criteria for ankyloglossia in children by anatomical measurements; to investigate the correlation between severity of ankyloglossia and a series of morphofunctional findings; to evaluate the potential mismatch between a clinical suspect of ankyloglossia and the authentic anatomical diagnosis.Design:  Two different techniques of anatomical measurements and a clinical evaluation of a series of morphofunctional findings were performed.Subjects and methods:  In 200 children referred for evaluation and treatment of tongue‐tie, the length of the frenulum and the interincisal distance were measured in maximum opening of the mouth and with the tip of the tongue touching the palatal papilla. Occlusion, type of bite, tongue resting position, swallowing mechanism, oral floor mobility, frenulum insertion modality and speech were investigated. Any correlation between these morphofunctional findings and anatomical measures was investigated.Results:  Children with a frenulum length more than 2 cm and an interincisal distance of more than 2.3 cm were normal. In both measurements, significant correlations among mean values and other variables were observed. Moreover, three levels – mild, moderate and severe – of ankyloglossia were assessed.Conclusions:  Length of frenulum and interincisal distance allow an assessment of severity of ankyloglossia in children. Ankyloglossia was not associated with infantile swallowing.