OBJECTIVES: Adenoid hypertrophy (AH) is a very common problem in children. Nasal Fiberoptic Endoscopy (NFE) represents the gold standard method to diagnose AH. Rhinomanometry represents a valid diagnostic support. The aim of our study was to analyze the grade of nasal obstruction caused by AH, in a group of children, with rhinomanometry standard and after ND test versus NFE. PATIENTS AND METHODS: Two hundred and eighty-four of 300 collaborative children, diagnosed as chronic oral breathers, were enrolled. All children underwent a complete physical examination, anterior active rhinomanometry and a second rhinomanometry after the administration of the nasal decongestant (ND) xylometazoline. All children were evaluated using Nasal Fiberoptic Endoscopy (NFE). RESULTS: At rhinomanometry nasal obstrucion was found of grade 1 in 102 (35.9%) children, of grade 2 in 41 (14.4%), of grade 3 in 52 (18.3%), of grade 4 in 37 (13%) and of grade 5 in 52 (18.3%). Those patients were tested also with rhinomanometry after ND: grade 1 in 108 (38%) children, grade 2 in 52 (18.3%), grade 3 in 56 (19.7%), grade 4 in 23 (8.1%) and grade 5 in 45 (15.8%). At NFE: 83 (29.2%) patients presented a grade 0, 73 (28.7%) a grade 1, 51 (17.9%), 34 (11.9%) a grade 3 and 43 (15.1%) a grade 4. Comparing the grade of nasal obstruction in NFE and in RM after ND we found a great correlation for grade 1 and grade 5 (respectively 84.3% and 79,1%, p < 0.001) and low correlation for the others grades of obstruction. When compared to NFE, rhinomanometry test after ND had 81.1% sensitivity and 84.3% specificity. Operating Characteristic (ROC) curves were derived using data related to rhinomanometry vs NFE, and to Rhinomanometry after ND vs NFE. CONCLUSIONS: Rhinomanometry after ND, compared to rmhinomanometry, is more specific and useful to evaluate nasal obstruction due to AH in children. RM after ND is a great tool to assess the severity of nasal obstruction. In fact, the minimum and maximum degrees of obstruction to the RM after ND correlate significantly (p < 0.01) with those of NFE