Background: Lateral neck radiograph is the most significant radiographic examination performed in a child with a suspected pharyngeal lesion. Methods: A 10-year-old boy suffered from severe sore throat with drooling and could not open mouth for 1 day. He complained of difficulty initiating swallowing even swallowing own saliva. Results: A lateral neck radiograph showed a mass shadow behind the posterior border of the mandibular ramus. Contrast-en- hanced CT showed a rim-enhanced hypodense mass (1.5 × 1.3 cm) at right superio-lateral tonsillar fossa. Endoscopy revealed a visible bulge of the right tonsil. Peritonsillar abscess was consequently diagnosed. Conclusions: A properly positioned lateral neck radiograph with a good imaging quality is a useful modality in the preliminary diagnosis of peritonsillar abscess.