The goal of this prospective study is to investigate the correlation between allergen sensitivity and radiographic evaluation of adenoidal obstruction and tonsil size. A total of 82 children with upper airway obstructive symptoms were evaluated for their tonsil size. All patients underwent digital lateral soft tissue radiographs. Assessment of nasopharyngeal obstruction in radiographs was done according to the Cohen and Konak method. Skin prick tests with multitest applicator including 14 allergens were carried out to investigate their allergic background. All children reacted positive to at least one of the 14 allergens tested. We found a statistically significant correlation between tonsil size and skin prick tests (P < 0.01). However, there was no statistically significant correlation between the adenoid size and skin prick test results (P > 0.05). Although the degree of nasopharyngeal obstruction caused by adenoid hypertrophy does not increase with the degree of positivity to specific allergens in skin prick tests, allergic sensitivity may play an important role in children with tonsillar hypertrophy.