Acoustic rhinometry (AR), introduced a decade ago for assessment of the nasal airways of adults, has several attractive features relevant to application in a paediatric population. Its non-invasive nature, simplicity and rapidity are prime assets when examining infants and small children. Valid AR measurements can be obtained in a few seconds and require minimal co-operation. The striking consistency of AR studies of healthy subjects and the agreement with CT-derived and directly measured choanal dimensions are a strong indication of its reliability. Acoustic rhinometry optimised for infants and small children opens new perspectives and possibilities in the assessment of nasal airway dimensions and their relationship to pathological conditions in both the upper and the lower airways. The objective of this paper is to describe the advantages of AR in infants and children, but also point out its limitations and potential sources of error. Practical guidelines as to the measurement procedure and analysis and interpretation of AR-data are outlined.